Phys final

One morning you discover that a tire on your auto is in
need of air. As you add air to the tire, which of the
following statements is true? (Select all that apply.)
a)The number of moles of air in the tire decreases.
b)The density of the air in the tire is decreased.
c)The pressure of the air in the tire increases.
d)None of these are true.

If the atmospheric pressure is 15 lb/in2
, what is the
corresponding downward force on the top of a
horizontal square area 6 inches on each side?
a)90 lbs
b)15 lbs
c)540 lbs
d)zero

A child is drinking a liquid with a straw. Which of the
following statements is true?
a)Thick, viscous fluids are easier to drink with a straw
than thin, nonviscous liquids.
b)The fluid is being pulled up into the straw.
c)It is easier to use a longer straw than a shorter straw,
because liquid weight increases the pressure at the
bottom.
d)When the pressure in the straw is reduced, atmospheric
pressure on the surface of the liquid pushes the liquid up
the straw.

A sharp knife can more easily cut objects than can a dull
knife because
a)sharp knives have edges that can fit between the
molecules of the object.
b)a greater force can be applied with a sharp knife.
c)a greater pressure can be applied with a sharp knife.
d)dull knives cannot apply large forces.

An ice cube in a glass of water is pushed to the
bottom of the glass and held there with a straw.
Consequently, the buoyant force on the ice cube is
now
a)greater than when the cube was floating at the top.
b)exactly balanced by the weight of the ice cube
c)exactly balanced by the force exerted by the straw.
d)the same as when the cube was floating at the top.

A boat floating in a large pool is loaded with solid
iron bars. The water level at the pool's edge is marked
with a red line. The iron is now thrown overboard.
When the water becomes calm again,
a)the red line is still at the water level.
b)the red line is slightly lower than the water level.
c)the red line is slightly higher than the water level.

A gas originally occupies a volume of 0.5 m3
at a
pressure of 100 kPa. It is slowly allowed to expand
until the volume is 2.5 m3
. Assuming the temperature
is kept constant, the final pressure will be
a)500 kPa.
b)50 kPa.
c)20 kPa.
d)100 kPa.
e)10 kPa.

A hydraulic jack is used to lift a load of weight 1000
N. The load-bearing cylinder has a radius of 4 cm, and
the other piston has a radius of 1 cm. What force must
be exerted on the smaller piston to support the load?
a)4000 N
b)250 N
c)125 N
d)1000 N
e)62.5 N

Three individuals stand with all of their weight on the
heel of one foot: a man of weight 600 N and a heel area
of 100 cm2
, a child of weight 200 N and a heel area of
25 cm2
and woman of weight 450 N and a heel area of
2 cm2
. The one exerting the least pressure on the
ground is
a)the man.
b)the child.
c)the woman.
d)all exert the same.

Archimedes Principle states that
a)the velocity of a fluid is directly proportional to the
pressure exerted on the fluid.
b)the pressure in a fluid is directly related to the depth
below the surface of the fluid.
c)the pressure of a fluid is inversely proportional to
the temperature of the fluid.
d)an object immersed in a fluid is buoyed up by a
force equal to the weight of the displaced fluid.

A child blows up a balloon with air. This balloon will
not float to the ceiling because
a)the balloon and the air it contains weigh more than the
air displaced by the balloon.
b)the pressure of the air inside the balloon is less than
the atmospheric pressure.
c)the pressure of the air inside the balloon is greater
than the atmospheric pressure.
d)the temperature of the air inside the balloon is less
than the atmospheric temperature.
e)the weight of the balloon is less than the weight of the

A balloon inflated with helium is able to float toward
the ceiling because
a)the balloon and the gas it contains weigh less than the
b)the pressure of the gas inside the balloon is greater
than the atmospheric pressure.
c)the density of the gas inside the balloon is greater than
the density of the atmosphere.
d)the pressure of the gas inside the balloon is less than
the atmospheric pressure.
e)the weight of the balloon is greater than the weight of
the air displaced by the balloon.

pool's edge is marked with a red line. The blocks are
now thrown overboard and float outside the boat.
When the water becomes calm again,
a)the red line is slightly lower than the water level.
b)the red line is still at the water level.
c)the red line is slightly higher than the water level.

An iceberg is floating in the ocean with 10% of its
volume extending above the ocean's surface. What
can you say about the iceberg?
a)Its density is 90% that of the ocean water.
b)It displaces only 90% of its weight in water.
c)Its weight is greater than the water it displaces.
d)It must be resting on the bottom, since ice can't float
in salt water.

In U.S. customary units, air pressure is measured in
pounds per square inch. In the metric system, it is
measured in Pascals, and one Pascal is equal to
a)one metric ton per hectare.
b)one pound per square foot.
c)one newton per square centimeter.
d)one newton per square meter.
e)None of these.

The density of ice is about 900 kg/m3
, and the
density of water is about 1000 kg/m3
. A cubic block
of ice one meter on a side floats in water. Assuming
that the lowest square face of the cube is horizontal,
the height of the block above the water line is
a)0.9 m.
b)0.1 m.
c)0.2 m.
d)0.8 m.
e)0.5 m.

Three horses are side-by-side on a merry-go-round:
one at the edge, one near the axis, and one in
between. Each horse has the same angular speed.
Which horse has the greatest linear speed?
a)The horse in the middle
b)The linear speed is the same for all three horses.
c)The horse nearest the axis
d)The horse at the edge

A torque acting on a body tends to produce
a)linear velocity.
b)a new center of gravity.
c)equilibrium.
d)angular rotation.

The rotational inertia of an object depends on
which of these?
a)None of the above.
b)Its color
c)How its mass is distributed about the spin axis
d)The amount of torque applied to it
e)How fast it is spinning

Using a longer handled wrench to loosen a tight nut
allows you to
a)increase the moment of inertia of the nut.
b)pull harder on the wrench.
c)exert more force on the nut.
d)apply more torque to the nut.

A figure skater is spinning with her arms
extended. She now pulls her arms close to her
body. What happens?
a)Her moment of inertia decreases
b)Her angular momentum increases
c)Her angular momentum decreases
d)Her moment of inertia increases

A dancer begins performing a pirouette with arms
extended. (A pirouette is a complete spin about a
vertical axis.) This motion is completed most easily
when the rotational inertia is decreased by
a)bringing the arms and legs in a line with the body.
b)ending at the waist at a right angle.
c)extending the arms and one leg straight out to the
sides.
d)holding the arms straight up and extending one
foot straight out to the side.

Because the rotational inertia is higher, it is hardest
in springboard diving to perform a forward
somersault in
a)the pike position (bending at the waist but not the
knees).
b)the straight position (no bending at knees or
waist).
c)the tuck position (bending at both the waist and
knees).

A constant torque is applied to a flywheel. Which of
the following mechanical quantities will be constant?
a)rotational velocity
b)rotational acceleration
c)angular momentum
d)linear velocity of a particle on the rim
e)rotational energy

In using a long steel rod as a lever to move a large
rock, where should the fulcrum be placed?
a)Anywhere in between - it makes no difference.
b)Close the point where the force is applied.
c)Close to the rock.
d)Halfway between the rock and the applied force.

The angular momentum of a rotating body is
conserved when
a)when a shape of the body does not change.
b)when the body has a constant angular
acceleration.
c)no net force acts on the body.
d)no net torque acts on the body.

A body of rotational inertia 1.0 kg m2
is acted upon
by a torque of 2.0 Nm. The angular acceleration of
the body will be
a)2.0 rad/s2
.
b)0.5 rev/s2
.
c)2.0 rev/s2
.
d)0.5 rad/s2
.
e)1.0 rad/s2
.

Which of the following is an appropriate unit for
describing rotational acceleration?
a)rev/min2
b)rad/min
c)rev/m/s
d)m/s2
e)rev/min

A student plays on a see-saw with her father. The
student has a weight of 250 N and is seated 2.4 m
from the axis of rotation. Her father balances her
when he is seated 0.8 m from the axis. The father's
weight is
a)500 N.
b)667 N.
c)725 N.
d)250 N.
e)750 N.

Torque in the metric system is measured in units of
a)N · m.
b)N · s.
c)N/m.
d)N.
e)N · rad.

If the net force on a body is zero, the net torque on
the body is
a)always zero.
b)certainly not zero.
c)not necessarily zero.

An isolated object is initially spinning at a
constant speed. Then, although no external forces
act upon it, its rotational speed increases. This
must be due to
a)impossible, angular momentum conservation is
violated.
b)an increase in the moment of inertia.
c)a decrease in the moment of inertia.
d)an increase in the angular momentum.
e)an increase in the mass.

The bigger gears on the rear wheel of a multi-speed
bike allow the rider to
a)increase the moment of inertia of the wheel.
b)decrease the moment of inertia of the wheel.
c)exert more force on the wheel.
d)exert more torque on the wheel.

The angular momentum of an isolated object can be
changed only by
a)changing its rotational inertia.
b)applying a force along the axis of rotation.
c)applying a torque.

When a bicycle pedal is at the top of its motion,
you can exert the greatest torque on the crank by
a)hooking your toes under the pedal and pulling
upward.
b)pushing straight down on the pedal with your
foot.
c)pushing straight forward on the pedal with your
foot.

A flywheel is used to minimize changes in rotational
velocity as the torque or the load changes. The
rotational inertia of a flywheel should be chosen to
be
a)as small as possible.
b)as large as possible.
c)anything - it doesn't matter.

When an ice skater twirling on the point of a skate
draws her arms in she ends up whirling faster. This
is because
a)a net torque acts on the skater.
b)linear momentum is conserved.
c)angular momentum is conserved.
d)rotational energy is conserved.

The rotational velocity of a 45 rev/min phonograph
record in rad/s is approximately
a)4.7 rad/s.
b)283 rad/s.
c)15.7 rad/s.
d)45 rad/s.
e)0.75 rad/s.

The armature of a motor is accelerated uniformly
from rest to a rotational velocity of 1800 rev/min in
10 seconds. The rotational acceleration of the
motor is
a)180 rad/s2
.
b)90 rad/s2
.
c)zero.
d)18.8 rad/s2
.
e)37.7 rad/s2
.

A wheel is spinning on an axle. The linear velocity
of a point on the rim is the product of the radius
times the rotational velocity, if the latter is measured
in units of
a)rev/s.
b)rad/s.
c)deg/min.
d)deg/s.
e)rev/min.

A merry-go-round, having a radius of 2.0 m, is set in
motion by students applying a force of 500 N
tangential to the rim of the wheel. The merry-go-
round reaches a rotational velocity of 2.0 rad/s after
10 seconds, starting from rest. The rotational inertia
of the merry-go-round is
a)5.0 104 kg · m2
b)5.0 105 kg · m2
c)5.0 103 kg · m2
d)1.0 105 kg ·
e)1.0 104 kg · m2

A bicycle exhibits greater stability when the angular
momentum of the wheels is
a)smaller.
b)larger.
c)any value.

If the net torque on a body is zero, the net force on
the body is
a)always zero.
b)not necessarily zero.
c)certainly not zero.

A student releases a ball from rest on an inclined plane and
measures that it travels a distance of 0.5 m in a time of 2.0
s. The average speed of the ball is:
a)1.0 m/s.
b)0.5 m/s.
c)2.0 m/s.
d)0.25 m/s.

A student releases a ball from rest on an inclined plane
and measures that it travels a distance of 0.5 m in a time
of 2.0 s. The acceleration of the ball is:
a)0.5 m/s2
.
b)0.125 m/s2
.
c)1.0 m/s2
.
d)0.25 m/s2
.

3. An auto moves 10 meters in the first second of
travel, 10 more meters in the next second and 10 meters
during the third second. The acceleration of the auto in
m/s2
is:
a)30
b)Zero
c)3.33
d)9.8
e)10

A car travels a distance of 80 km. For the first 30
minutes it is driven at a constant speed of 80 km/h.
The motor begins to vibrate and the driver reduces the
speed to 40 km/h for the rest of the trip. The average
speed for the entire trip is:
a)47.5 km/h.
b)53.3 km/h.
c)60.0 km/h.
d)50.0 km/h.
e)40.0 km/h.

A car is driven between two nearby towns at an average
speed of 50 miles/hour. The magnitude of the average
velocity of the car:
a)will be the same as or less than the average speed.
b)will be the same as or greater than the average speed.
c)will always be the same as the average speed.
d)will always be less than the average speed.
e)will always be greater than the average speed.

A car starts from rest and reaches 20 m/s in 10
seconds. The average acceleration of the car in m/s2
is:
a)Zero
b)4.0
c)1.0
d)2.0
e)10.0

Which of the following is not an appropriate unit for
measuring acceleration?
a)miles/hr/s
b)km/min/s
c)ft/s2
d)m/min2
e)m/s

A car rolls down an incline starting from rest. A graph
of position versus time is made for this motion. One
can get the:
a)distance traveled from the slope of the graph.
b)velocity from the area under the graph.
c)acceleration from the slope of the graph.
d)instantaneous velocity from the slope of the graph.
e)acceleration from the area under the graph.

A car is traveling at the velocity of 20 m/s on a flat road
when it reaches the bottom of a hill. It coasts up the hill,
coming to rest in 4 seconds. The average acceleration of
the car while on the hill is:
a)120 m/s2
.
b)0 m/s2
.
c)-5 m/s2
.
d)5 m/s2
.
e)-20 m/s2
.

Which of the following quantities relating to motion is
not a vector?
a)Velocity
b)Displacement
c)Average velocity
d)Speed
e)Acceleration

The velocity of a body is graphed as a function of time.
The slope of the graph at any point may be identified
with:
a)instantaneous velocity.
b)instantaneous speed.
c)average velocity.
d)instantaneous acceleration.
e)average acceleration.

A quantity that is a measure of how the distance
traveled changes with time is:
a)speed.
b)displacement.
c)momentum.
d)acceleration.
e)velocity.

A car is decelerating at the rate of 3 km/s2
. If its initial
speed is 66 km/s, how long will it take the car to come to
a complete stop?
a)220 s
b)192 s
c)2.2 s
d)22 s

If you drop a ball in the absence of air resistance, it
accelerates downward at 9.8 m/s2. If instead you
throw the ball upward, then its acceleration after
release is
a)less than 9.8 m/s2
.
b)equal to 9.8 m/s2
.
c)greater than 9.8 m/s2
.

After 1 second, a ball dropped from rest will have fallen:
a)9.8 m.
b)4.9 m.
c)1.0 m.
d)2.45 m.
e)19.6 m.

A ball thrown upward reaches its maximum height,
and then falls back. If air resistance is negligible, its
acceleration is:
a)the same at all points in the motion.
b)the same up and down but zero at the top.
c)less on the way up than on the way down.
d)less on the way down than on the way up.

A bullet is fired horizontally at a target 20 m away.
The velocity of the bullet as it leaves the gun is 100
m/s. How much, approximately, will the bullet drop
on its way to the target?
a)0.4 m
b)0.1 m
c)0.3 m
d)0.2 m
e)0.5 m

During the first 10 seconds after a ball is dropped from
rest, how far will it fall?
a)980 m
b)100 m
c)245 m
d)1960.0 m
e)490 m

A man standing on a bridge throws a stone horizontally
with a speed of 20 m/s. The stone hits the water below
3 s later. The bridge is:
a)30 m high.
b)60 m high.
c)45 m high.
d)20 m high.

A ball rolls off a shelf and hits the floor below 0.25
seconds later. To find the speed of the ball as it left the
shelf, we would need:
a)the height of the table.
b)to repeat the experiment.
c)the distance measured along the floor to the point of
impact.
d)the weight of the ball.

A ball is thrown across the street. During its flight, the
ball's speed is lowest at:
a)The end of its flight.
b)The beginning of its flight.
c)The highest point of its flight.
d)The speed is constant throughout the flight.

All except one of the following require the application of a
net force. Which one is the exception?
a)to change an object from a state of rest to a state of motion
b) to maintain an object in motion at a constant velocity
c)to maintain an object in uniform circular motion
d)to change an object's direction of motion without changing
its speed
e)to change an object's speed without changing its direction
of motion

A 100 pound sack of potatoes falls from an airplane. As
the velocity of the falling sack increases, so does the air
resistance on it. When the air resistance equals 100
pounds, the acceleration of the sack will be:
a)zero.
b)infinite.
c)9.8 m/s2
.
d)9.8 m/s.

A single constant 10 pound force F1 acts on a body,
causing it to accelerate. Then, while F1 continues to act, a
second constant force F2 is applied to the body, which
comes to a momentary stop. The magnitude of F2 is:
a)not enough information to tell.
b)zero.
c)exactly 10 pounds.
d)a bit less than 10 pounds.
e)larger than 10 pounds.

A car rounds a curve while maintaining constant speed.
The correct statement is:
a)The velocity of the car is zero.
b)A net force acts upon the car.
c)The acceleration of the car is zero.
d)No net force acts on the car.
e)The velocity of the car is constant.

An elevator of mass 500 kg is caused to accelerate
upward at 4.0 m/s2
by a force in the cable. What is the
force exerted by the cable?
a)6,900 N
b)zero
c)2,900 N
d)4,900 N
e)2,000 N

The starship Enterprise locks onto an alien ship (whose
mass is much greater than the Enterprise's mass) with its
tractor beam (think of this as a futuristic rope) and starts
to pull the alien ship toward it. Neither ship has its
propulsion engines running. Which ship has greater
acceleration towards the other?
a)the Enterprise
b)They both move with equal acceleration.
c)the alien ship
d)Neither ship can move because there is no friction in
outer space.

An elevator is being lifted upward at a constant speed by
a steel cable. All frictional forces are neglected. In this
situation, forces on the elevator are such that:
a)the upward force by the cable is equal to the
downward force of gravity.
b)the upward force by the cable is greater than the
c)the upward force by the cable is smaller than the
d)none of the above. (The elevator goes up because the
cable is being shortened, not because an upward force is
exerted on the elevator by the cable.)

Two bodies have quite different masses, but the net
force applied to each of them is the same. The
acceleration of:
a)each body is the same.
b)the less massive body is larger.
c)the more massive body is larger.

A body sliding on a table is observed to gradually slow
down. The correct statement is that the body slows
down because:
a)no net force acts on the body.
b)it is the nature of the body to slow down by itself.
c)a net force acts on the body.
d)no force acts on the body.

Two blocks of equal mass are connected by a string.
The system is accelerated across a smooth horizontal
surface by a force supplied by a rubber band connected
to the leading block. The tension in the connecting
string will be:
a)greater than the force pulling the leading block.
b)zero.
c)less than the force pulling the leading block.
d)the same as the force pulling the leading block.

The acceleration of gravity on the moon's surface is
about 1/6 of that on the Earth's surface. An object on
the Earth is to be taken to the Moon. We can state that,
compared to the Earth,
a)the object's mass will be less on the Moon.
b)the object's mass will be the same on the Moon.
c)the object's mass will be greater on the Moon.
d)the object's weight will be the same on the Moon.
e)the object's weight will be greater on the Moon.

A block of mass 5.0 kg is acted upon by a single
force, producing an acceleration of 2.0 m/s2
. The
force has a value of:
a)2.5 N.
b)0.5 N.
c)10 N.
d)5.0 N.

A 5.0 kg block on a smooth horizontal surface is acted
upon by two forces: a horizontal force of 40 N acting
to the right and a horizontal force of 10 N to the left.
The acceleration of the block will be:
a)8.0 m/s2
to the right
b)5.0 m/s2
to the right
c)6.0 m/s2
to the right
d)10.0 m/s2
to the right

A child, whose weight is 150 newtons, lifts a pumpkin
from the ground with a force of 50 newtons. The force
the pumpkin exerts on the child is:
a)zero.
b)more than 50 newtons.
c)50 newtons.
d)greater than zero but less than 50 newtons.

The surface gravity of Mars is 3.7 m/s2
. If a person with
mass of 100 kg were parachuting on Mars, what would
be the force exerted by air resistance at terminal
velocity?
a)100 N
b)980 N
c)370 N
d)490 N

Your mass is 50 kg. Suppose you are standing on a
scale in an elevator which starts moving up and
increases its speed at the rate of 2 m/s every second.
What would be the reading on the scale?
a)490 N
b)590 N
c)390 N
d)0
e)100 N

Your mass is 50 kg. Suppose you are standing on a
scale in an elevator, that is approaching a top floor
and decreasing its speed at the rate of 2 m/s every
second. What would be a reading on the scale?
a)590 N
b)390 N
c)490 N
d)0
e)100 N

A quarterback of mass 85 kg is running at 10 m/s.
Also, a tackle of mass 100 kg is running at 9 m/s.
a)The tackle has the greater kinetic energy.
b)The quarterback has the greater kinetic energy.
c)The quarterback and the tackle have equal kinetic
energies.

A child riding on a swing rises to a height 1.0 m above
the lowest point. Another child of equal mass whose
speed at the lowest point is twice as great will rise
a)to a height which depends on the mass.
b)four times as high.
c)twice as high.
d)to the same height.

A box is pushed across a rough horizontal floor by a force
acting parallel to the floor in the direction of motion. A
force doing negative work on the body is
a)friction.
b)a fictitious force.
c)the applied force.
d)gravity.
e)normal reaction force of floor upward on body.

In order for a body to exhibit simple harmonic motion
there must be
a)a force drawing the body toward the center and
increasing with distance away from the center.
b)a force drawing the body toward the center and
decreasing with distance away from the center.
c)a constant force pushing the body away from the
center.
d)a constant force drawing the body toward the center.
e)a force pushing the body away from the center and
increasing with distance away from the center.

Which of the following is not an energy unit?
a)calorie
b)watt
c)kWh
d)Joule
e)N m

Work is not being done on an object unless the
a)object is being accelerated.
b)object is moving.
c)speed is constant.
d)net force on the object is zero.

When work is done by a force on an object, then which
of the following are true?
a)The object does negative work on the force.
b)The work done will be equal to the change of the total
energy of the object plus energy appearing as heat, light,
or sound.
c)The energy lost to friction is equal to the amount of
work done by the force.
d)The mass of the object always increases.
e)The speed of the object always increases.

Suppose you climb the stairs of a ten-story building,
about 30 m high, and your mass is 60 kg. The
gravitational potential energy you gain is about
a)27000 Joule.
b)18000 Joule.
c)1800 Joule.
d)270 Joule.

A ball at the end of a string is swinging as a simple
pendulum. Assuming no loss in energy due to friction,
we can say for the ball that
a)the potential energy is maximum where the kinetic
energy is maximum.
b)the kinetic energy is maximum at each end of the
motion.
c)the potential energy is maximum at the lowest
position of the ball.
d)the potential energy is maximum where the kinetic
energy is a minimum.

Which of the following is not a unit of power?
a)horsepower
b)kilowatt-hour
c)watt
d)joule/second
e)kilowatt

Object A moving due east collides with object B moving
due west. After the collision, A is moving 20° north of
due east. What must be true of B after the collision?
a)At least part of B's velocity must be toward the south.
b)B must be moving 20° south of due east.
c)At least part of B's velocity must be toward the west.
d)B must be moving 20° south of due west.
e)none of these

A 20 kg child runs at 4.0 m/s and jumps onto a
shopping cart, which also has mass 20 kg. Assuming
the child rides on the cart after the collision, the speed
of the child and shopping cart, just after the child
jumps on, is
a)2.0 m/s.
b)zero.
c)3.0 m/s.
d)4.0 m/s.

Two people sit face to face on chairs which are free to
roll without friction. They push each other with a force of
50 N and move apart. Person A, whose mass (including
the chair) is 80 kg, moves to the left at 2.5 m/s. Person B,
whose mass (including the chair) is 50 kg,
a)moves to the right at 10 m/s.
b)moves to the right at 4 m/s.
c)moves to the right at 3.16 m/s.
d)moves to the right at 2.5 m/s.

In a head-on automobile collision, a person's momentum
could be reduced from 2000 kg m/s to zero in just 0.1 s.
If this occurs, the average force exerted to stop the
person is
a)Can't answer without knowing the person's mass.
b)200 N.
c)2,000 N.
d)20,000 N.

A 4 kg block, initially moving due east at 3 m/s, is
acted upon by an impulse having magnitude 8 Ns and
direction due west. The final velocity of the block is
a)2 m/s west.
b)8 m/s west.
c)3 m/s east.
d)1 m/s east.

Which of these collisions is likely to be most nearly
elastic?
a)Two steel balls collide at low speed.
b)Two steel balls collide at high speed.
c)A steel ball collides with a cotton ball at high speed.
d)A steel ball collides with a cotton ball at low speed.

Suppose a ball is dropped from shoulder height, falls,
makes a perfectly elastic collision with the floor, and
rebounds to shoulder height. Compare the magnitudes of
the impulses delivered to the ball by gravity and by the
floor during this entire motion.
a)The impulse delivered by the floor is twice as large as
the impulse delivered by gravity.
b)The floor delivers an upward impulse, but gravity does
not deliver a total impulse.
c)The two impulses have the same magnitude.
d)The impulse delivered by the floor is half as large as
the impulse delivered by gravity.

A bullet is fired into a wall and comes to rest.
Considering the bullet as the system we can say that
a)the total kinetic energy is conserved.
b)both total kinetic energy and momentum are
conserved.
c)neither total kinetic energy nor momentum are
conserved.
d)the momentum is conserved.

The purpose of an air bag in an auto is to
a)increase your body's stopping time during a collision.
b)reduce your speed just before a collision.
c)reduce the need for good brakes on your car.
d)increase the force applied to you during a collision.

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