The figure shows a ball with mass m = 0.471 kg attached to the end of a thin rod with length L = 0.582 m and negligible mass. The other end of the rod is pivoted so that the ball can move in a vertical circle. The rod is held horizontally as shown and then given enough of a downward push to cause the ball to swing down and around and just reach the vertically upward position, with zero speed there. How much work is done on the ball by the gravitational force from the initial point to (a) the lowest point, (b) the highest point, and (c) the point on the right level with the initial point? If the gravitational potential energy of the ball-Earth system is taken to be zero at the initial point, what is it when the ball reaches (d) the lowest point, (e) the highest point, and (f) the point on the right level with the initial point? L

PHYS 111 W24: Tutorial Quiz #6 Problem 1: A skier of mass 70 kg if pulled up a slope by a motor-driven cable. (a) How much work is required to pull him 60 m up a 30 degree slope (frictionless) at a constant speed of 2 m/s? (b) What power must a motor have to perform this task? Problem 2: Three ice skaters meet at the center of a rink and each stands at rest facing the center, within arm's reach of the other two. On a signal, each skater pushes themselves away from the other two across the frictionless ice. After the push, Skater A with mass 80 kg moves in the negative y-direction at 3.5 m/s and skater B with mass 75 kg moves in the negative x-direction at 4 m/s. Find the x- and y-components of the 90 kg Skater C's velocity after the push. Assume a birds-eye view of the situation for your coordinates.

A box m = 85 kg is being pulled by a constant force F = 150 N at an angle of θ= 25 degrees. The initial speed of the box is zero.  How much work, in joules, is done by the normal force as the block moves 3.9 m?

Consider a satellite in a circular orbit above Earth’s surface. In Chapter we will learn that the force of gravity changes only the direction of motion of a satellite in circular motion (and keeps it in a circle); it does NOT change the satellite’s speed. Work done on the satellite by the gravitational force is zero. What is your explanation?