PRACTICE PROBLEMS III

1. Suppose a gymnasium mat rests on the floor with a child sitting on the mat. The child and mat together weigh 22.73 N. If the coefficient of static friction between the mat and floor is 0.15, what is the maximum force that can be developed?
2. How fast must a halfback (77.27 kg) run to gain sufficient momentum to stop a fullback (90.9 kg) running at 7.62 m/s with a head-on tackle?
3. Which of the following series of values is most likely to represent, respectively, the coefficients of restitution for a superball, a tennis ball, and a softball from a height of 2 m onto a concrete floor?

a. 0.92, 0.75, 0.94

b. 5.86, 3.21, 1.65

c. 0.31, 0.67, 0.89

d. 0.92, 0.75, 0.36

e. 0.45, 3.21, 5.86

4. A ball dropped on a surface from a 2.5 m height bounces to a height of 0.77 m. What is the coefficient of restitution between the ball and the surface?