A simple pendulum (a mass swinging at the end of a string) swings back and forth in a circular arc. What is the direction of the acceleration of the mass when it is at the ends of the swing? At the midpoint? In each case, explain how you obtained your answer.

Solution 1DQ At the end of the swings the bob reverses its direction. So, let’s calculate the accelerations just before reaching the maximum height and just after leaving the maximum height. Step 1: When the bob moves upwards and approaches the the maximum height, the acceleration is opposite to the direction of motion as the force is a restoring force. The acceleration is tangential to the arc but opposite to the motion. When the bob reaches the maximum height and reverses the direction, the acceleration is tangential to the arc and in the same direction of velocity.