1. A sprinter with a mass of 55 kg is running at a speed of 3.8 m/s. In a burst of speed to win the race, she increases her speed to 5.9 m/s. Determine the work that the sprinter does to increase her speed.
2. A 35 g tennis ball approaches a player horizontally at a speed of 7.0 m/s. The player hits the ball with a racquet in a collision that lasts 5.0 ms. To return the ball with a horizontal speed of 9.0 m/s, how much average force must the player apply?
3. 3. Is the elastic potential energy stored in a spring greater when the spring is stretched by 3 cm or when it is compressed by 3 cm? Explain your answer.
4. Two people are riding inner tubes on an ice-covered (frictionless) lake. The first person has a mass of 65 kg and is travelling with a speed of 5.5 m/s. He collides head-on with the second person with a mass of 140 kg who is initially at rest. They bounce apart after the perfectly elastic collision. The final velocity of the first person is 2.1 m/s in the opposite direction to his initial direction. (a) Are momentum and kinetic energy conserved for this system? Explain your answer. (b) Determine the final velocity of the second person. please show me steps