Physics 1100 In-Class Problems: Collisions & Momentum

1. The diagrams below are graphs of Force in kiloNewtons versus time in milliseconds for the motion of a 5-kg block moving to the right at 4.0 m/s.
   (a) What is the magnitude and direction of the impulse acting on the block in each case?
   (b) What is the magnitude and direction of the average force acting on the block in each case?
   (c) What is the magnitude and direction of the final velocity of the block in each case?
   
2. The diagrams below are the velocity versus time graphs for the collision of motion of a 4-kg block with a wall. The collision lasts for 20 milliseconds in each case.
   (a) What is the magnitude and direction of the impulse acting on the block in each case?
   (b) What is the magnitude and direction of the average force acting on the block in each case?
   
3. You've been rowdy and obnoxious in a bar and now are in the process of being thrown out by the bouncer by the scruff of the neck. The bouncer has hold of you for 5.0 s and you are given a final velocity of 2.75 m/s. If your mass is 70.0 kg, what was your final momentum? What impulse and average force did the bouncer exert on you? Assume all motion is in a straight line.

4. A ball of mass 0.500 kg with speed 15.0 m/s collides with a wall and bounces back with a speed of 10.5 m/s. If the motion is in a straight line, calculate the initial and final momenta and the impulse. If the wall exerted a average force of 1000 N on the ball, how long did the collision last?

5. A ball of mass 0.25 kg glances of a wall as shown in the diagram. The ball approaches at 15 m/s at θ = 30° and leaves at 12 m/s at φ = 20°. The collision lasts for 15 milliseconds.
   (a) What are the components of the impulse experienced by the ball?
   (b) What are the components of the average force acting on the ball?
   
6. While chasing an armed suspect into and onto an ice rink, a police constable is shot. Fortunately, the constable is wearing a bullet-proof vest which absorbs the bullet. If the muzzle velocity of the bullet is 350 m/s and the its mass is 100 g. Find the final velocity of the constable and bullet if her mass is 69.5 kg. Assume all motion is in a straight line and ignore friction. Assume that the constable is at rest.
   

7. A 70-kg man and a 55-kg woman are standing on a stationary sled which is on a frictionless surface. The man jumps horizontally off the sled with a velocity of 3.00 m/s at 25.0° west of north. The woman jumps off the sled horizontally with a speed of 3.25 m/s at 40.0° south of west. What is the magnitude and direction of the sled's final momentum? If the mass of the sled is 7.50 kg, what is the final velocity of the sled?
   

8. A 50.0-kg skater is travelling due east at a speed of 3.00 m/s. A 70.0-kg skater is moving due south at a speed of 7.00 m/s. They collide and hold on to one another after the collision, managing to move off at an angle θ south of east with a speed v_f. Find (a) the angle θ and (b) the speed v_f, assuming that friction can be ignored.
   

9. Two opposing hockey players are racing up the ice for the puck when they collide at point A as shown in the diagram below. The first hockey player has mass 90 kg and a speed of 2.7 m/s while the other has mass 82 kg and speed 3.1 m/s. The angle in the diagram is θ = 32°. After the collision, the players remain locked together (at least until the referee forces them apart). What is the magnitude and direction of the players' velocity just after they collide?
   
   

10. In a curling match, a 6.0-kg rock with speed 3.50 m/s collides with another motionless 6.0-kg rock. What are the velocities of the rocks after the collision if it is (a) elastic or (b) totally inelastic? Ignore friction and assume all motion is in a straight line.

11. A 5.00-kg ball, moving to the right at a velocity of +2.00 m/s on a frictionless table, collides head-on with a stationary 7.50-kg ball. Find the final velocities of the balls if the collision is (a) elastic and (b) completely inelastic.
    

12. A 60.0-kg person, running horizontally with a velocity of 3.80 m/s jumps on a 12.0-kg sled that is initially at rest. (a) Ignoring the effects of static friction, find the velocity of the sled and person as they move away. (b) The sled and person coast 30.0 m on level snow before coming to a rest. What is the coefficient of kinetic friction between the sled and the snow?
    

13. A 5.0-kg block slides from rest down an L = 2.50 m long 25° incline. At the bottom it undergoes an elastic collision with a 10.0-kg block sending it towards a 35° incline. After the collision, how far along its incline does each block go. The surface is frictionless.
    
    

Questions? mike.coombes@kwantlen.ca