Two football players collide head-on in midair while trying to catch a thrown football and cling together. The first player is 90 kg and has an initial velocity of 7 m/s, while the second player is 119 kg and has an initial velocity of −6 m/s. Ignore air resistance and friction. What is their velocity vf just after impact if they cling together? In the next three parts, (d) through (f), justify that friction could be ignored compared to the forces of collision by considering the change in momentum of the first player. Let's assume that the collision lasts for 10ms. Calculate the force on the first player by the second player during the collision. (d) Calculate the magnitude of the force resulting from the change in the player's velocity during the collision: (e) Calculate the force due to the weight of the player

A 0.25-kg ball, initially at reston a tee, is hit with a bat in the x-direction while 1.00 meter above the ground. If the ball hits the ground 20 meters away and was in contact with the bat for 0.10-s, what average force was exerted on the ball during the contact time?   Answer: 111 N

When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 69.5-kg man just before contact with the ground has a speed of 8.82 m/s. (a) In a stiff-legged landing he comes to a halt in 4.17 ms. Find the magnitude of the average net force that acts on him during this time. (b) When he bends his knees, he comes to a halt in 0.267 s. Find the magnitude of the average net force now. (c) During the landing, the force of the ground on the man points upward, while the force due to gravity points downward. The average net force acting on the man includes both of these forces. Taking into account the directions of the forces, find the magnitude of the force applied by the ground on the man in part (b).

A 0.11 kg apple falls off a tree branch that is 2.2 m above the thick grass. The apple sins 0.065 m into the grass while stopping. Determine the average contact force that the grass alone exerts on the apple while stopping it. Ignore air resistance.