A car moving at 10 m/s crashes into a barrier and stops in 0.50 s. There is a 20 kg child in the car. Assume that the child's velocity is changed by the same amount as the car's in the same time period.
a. What is the impulse needed to stop the child?
b. What is the average force on the child?
c. What is the approximate mass of an object whose weight equals the force in part b?
d. Could you lift such a weight with your arm?
e. Why is it advisable to use a proper restraining seat rather than hold a child on your lap?