PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A 2.0kg cart (Cart A) moves along a straight, frictionless track at +1.5ms−1. Farther down the track, a 3.0kg cart (Cart B) moves in the same direction at +0.50ms−1. At the instant shown, a 1.0kg block (Block C) is dropped vertically onto Cart A and sticks to it without affecting Cart A’s horizontal speed at the moment of contact.
Assume the block’s vertical motion does not impart any horizontal impulse to the system.
(a) Determine the velocity of the center of mass of the system consisting of Carts A and B just before the block is dropped.
(b) Calculate the velocity of the center of mass of the enlarged system (Carts A and B plus Block C) immediately after the block sticks to Cart A.
(c) Explain, without additional calculation, whether the CM velocity you found in part (b) will change in the subsequent time interval before Cart A catches up to Cart B. Justify your answer in terms of external horizontal forces.