11. In boxing matches in the nineteenth century, boxers fought with bare hands. Today's boxers use padded gloves. (a) How do gloves help protect a boxer's head (and brain) from injury? (b) Boxers often "roll with the punch." Use physics principles to explain how this maneuver helps protect them. 10. Determine the impulse imparted during the interaction represented in each graph in Figure 4. (a) (b) 60 7 2 40 F (N [E]) F (N [SD) 20- 0.1 0.2 0.3 0.4 0.5 0.2 0.4 0.6 0.8 1.0 t (s) t (s) [(a) 1.0 N.s [E]] [(b) about 40 N.s [S]] 6. A snowball of mass 65 g falls vertically toward the ground where it breaks apart and comes to rest. Its speed just before hitting the ground is 3.8 m/s. Determine (a) the momentum of the snowball before hitting the ground [0.25 kg.m/s [down]] b) the momentum of the snowball after hitting the ground [zero] (c) the change in momentum [0.25 kg.m/s [up]] 7. A truck's initial momentum is 5.8 x 10* kg.m/s [W]. An average force of 4.8 x 103 N [W] increases the truck's momentum for the next 3.5 s. (a) What is the impulse on the truck over this time interval? [1.7 x 10* N.s [W]] (b) What is the final momentum of the truck? [7.5 x 10* kg.m/s [W]] 8. A 0.27-kg volleyball, with an initial velocity of 2.7m/s horizontally, hits a net, stops, and then drops to the ground. The average force exerted on the volleyball by the net is 33 N [W]. How long, in milliseconds, is the ball in contact with the net? [22 ms] 9. In its approach to an airport runway, an airplane of mass 1.24 x 10 kg has a velocity of 75.5 m/s [11.1' below the horizontal]. Determine the horizontal and vertical components of its momentum. [9.19 x 10 kg.m/s; 1.80 x 10 kg.m/s]