Question

This lab uses three friction carts with different surfaces on the bottom (cork, felt, and Teflon) and a set of masses totaling 1250 g. The carts are pulled with a piece of string attached to a hook on a force sensor, which measures the force of tension in the string. Behind the cart being pulled is a motion sensor. These two devices are used to display and record the string tension and the velocity of the cart as a function of time, with a 20 Hz (measurements per second) sampling rate. The main use for the velocity vs. time graph is to allow the person pulling the cart to make sure that, once the cart starts to move, they are pulling the cart with the constant force required to maintain a constant velocity.

1. Before the cart starts moving, what is the net force on it? How is the (horizontal) string tension force acting on the cart related to the friction force acting on the cart?

2. When the cart is moving with a constant velocity, what is the net force on it? How is the (horizontal) string tension force acting on the cart related to the friction force acting on the cart?

Answer 1