1. In a chain reaction car accident on the North-South tollway, a BMW with a mas
ID: 1700499 • Letter: 1
Question
1. In a chain reaction car accident on the North-South tollway, a BMW with a mass of 2000 kg collides elastically with a Honda Civic (mass 1500 kg) at rest. The Honda in turn collides with a Hummer of mass 3000 kg in front of it, that’s also at rest, and the Honda and the Hummer lock bumpers and slide forward with a velocity of 3 m/s. (The BMW that originated the chain of events is not involved in the second collision). What was the velocity of the Honda right after the first collision and before it hits the Hummer?2. With regard to the BMW-Honda-Hummer collision problem, what was the velocity of the BMW right before the first collision?
3. With regard to the BMW-Honda-Hummer collision problem, what was the velocity of the BMW right after its collision with the Honda?
4. With regard to the BMW-Honda-Hummer collision problem, what is the net impulse on the "isolated system" during the first collision event?
5. A figure skater spinning with an angular velocity of 20 rpm in the close position (arms, legs close to her axis of rotation) extends her arm and legs and increases her moment of inertia to 5 times her original value. As a result of this, the angular momentum of the skater:
a. increases by a factor of 5
b. decreases by a factor of 5
c. stays the same
d. cannot tell
6. A 5 kg bowling ball of radius 10 cm rolls on a level surface with a velocity of 5 m/s. What is the total kinetic energy of the ball? Give your answer as a number expressed in units of Joules but do not enter units into the answer box.
Explanation / Answer
1. conservation of momentum. 3*(3000+1500)=v*1500. so v=9(m/s). 2. assume that velocity of the BMW is v. we have v1=v, v1'=v'. v2=0. v2'=9. v2'=(v2*(m2-m1)+2m1*v1)/(m1+m2). so that v2'=2m1v1/(m1+m2). so v1=7.9(m/s) 3.we have v1'=(v1*(m1-m2)+2m2v2)(m1+m2)=1.125(m/s) 4.zero 5.decrease by 5 times. 6. moment of inertia. I=2Mr^2/5+Mr^2=7Mr^2/5=0.07(kgm2). w=5/0.1=50(rad/s). so E=Iw^2/2=87.5(J)
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