PHYSlZ30: General Physics Problems Name: Date Practice 9: Energy 8: Impulse A superball of mass m = 0.2 kg is thrown straight up into the air starting from a height yo = 2.3 m above the ground. The ball reaches a maximum height ymax = 5 m above the ground. After the ball hits the ground, it bounces back up to a new maximum height equal to (2/3) ymax. Assume the collision with ground takes place over a time Atcomsion = 0.1 s. ) The above process is represented in the figure to the right. The important states of the ball are labeled: ymax BO 2/3 W Astarting point of the ball: y E O B maximum height of the ball: C when the ball just hits the ground (moving down): D when the ball just bounces from the ground (moving up): E new maximum height of the ball. ground Conceptual analysis: Gravitational force acts on the ball, which is a conservative force, thus we expect conservation of energy as long as the ball is not in contact with the ground. 1. What was the magnitude of the initial velocity vo of the ball when it was released? Hint: Consider all the energy of the ball at positions A and B. 2. What was the change in the kinetic energy of the ball due to the collision of the ball with the ground? Hint: Analyze conservation of energy during the ball's trajectory. PHYS1230: General Physics Problems 3. What impulse did the ground impart to the ball? (Remember that impulse is a vector). 4. What was the average force of the ground on the ball during the collision