1.
Curved Motion Diagram Learning Goal: To understand the relation between acceleration and
velocity change by focusing on velocity as a vector. The motion diagram shown in the figure
represents a pendulum released from rest at an angle of 45 degree from the vertical. The dots in
the motion diagram (Figure 1) represent the positions of the pendulum?s bob at eleven moments
(labeled 0 through 10) in time; the black arrows between adjacent dots (moments) represent the
average velocities. Equal time intervals separate the dots. Also given is a ''compass rose'' in
which directions are identified by letters of the alphabet. Part A - Acceleration of the bob at the
fifth moment What is the acceleration?s direction at moment 5? Reference the compass rose and
enter the letter that identifies the direction of deltav, the velocity change. Enter Z if the
acceleration vector has zero length. Z ________________ Part B - Direction of the bob?s
acceleration at the zeroth and tenth moments What are the directions of the bob?s accelerations
at moments 0 and 10? Reference the compass rose and enter the letters that identify the
directions of the accelerations at moments 0 and 10 separated by a comma. Enter Z if an
acceleration vector has zero length. moment 0, moment 10 = D, F
Solution
Answer: A
Since , At moment 5 Force acting are Normal and Gravity , both acting in Vertical direction
only therfore accleration can be only in vertical direction.
Now, since bob is moving in circular path there will be always a centripital accleration
towards the centre, which cause the change of direction of velocity vector.