Group Problem #16 Physics 111-4 (and 3) Spring 2012 Page 1 of 6
Group problem set #16: Collisions and impulse
Since you are an expert at Karate, you are doing a demonstration for beginning students. With an expert blow of your hand, you shatter a concrete block. Assuming your hand has a mass of 0.7kg and is moving at 5 m/s as it strikes the block and that your hand stops 6mm beyond the point of contact: A) What impulse does the block exert on your hand? B) What is the approximate amount of collision time? C) What is the average force the block exerts on your hand?
In a feat of public marksmanship, you fire a bullet into a hanging wood block, which is a known as a ballistic pendulum. The block, with the bullet embedded, swings upward. Noting the height reached at the top of the swing (h), you immediately inform the crowd of the bullet’s speed. How fast was the bullet traveling? (Mechanical energy is near enough to being conserved in this situation that you may consider it conserved.)
While driving to work one morning, you are witness to a car accident. A 14,000kg truck and 200kg car have a head-on collision. Despite attempts to stop, the truck has a speed of 6.6 m/s when they collide and the car has a speed of 8.8 m/s. If 10% of the initial total kinetic energy is dissipated through damage to the vehicles, what are the final velocities of the truck and the car after the collision?
You are testing collisions for a car manufacturer for a summer job. In your lab, on an air track, you send a 0.4kg mass, m1, at 3.0 m/s in the positive direction. It approaches a stationary mass, m2, of 0.8kg. They collide and, after the collision, the velocity of m2 is 1.6 m/s in the positive direction. For your report, you need to determine the velocity of mass m1 after the collision. Is the collision elastic or inelastic? If the latter, what percentage of the maximum possible kinetic energy loss occurs?
Watching a baseball game, you decide to calculate the speed of a baseball after it is struck. The baseball has a mass of 0.15kg and is moving horizontally with a momentum of 4.0kg m/s is struck head on by a baseball bat with an impulse of 10 Ns.
While playing with your niece, a 440-gram ball rolls off the top of a bookcase from a height of 3.2m onto a hard surface and bounces back to exactly that height. Since you took Physics, you decide to calculate the impulse received by the ball. What is the average force on the ball during the 0.008s during which the ball was in contact with the floor?