Physics 011

A of PQ#7A

Chapter 7 : Linear Momentum
Practice Questions

1.	An Olympic diver dives off the high-diving platform. The magnitude of his momentum will be a maximum at point The correct answer: D The magnitude of momentum is speed times mass (constant). Review Section 7-1 in Giancoli.
2.	Which of the following can best be described as an elastic collision? The correct answer: A golf club striking a golf ball. The earth is dented, branches are broken. This is not elastic. Review Section 7-4 in Giancoli.
3.	The Center of Mass of which of the following objects would not lie within the body itself? The correct answer: frisbee Review Section 7-8 in Giancoli.
4.	What is the magnitude of the impulse as shown in the following figure? The correct answer: 900 Ns Review Section 7-3 in Giancoli.
5.	If the impulse is applied to a particle at rest what will be its final momentum? The correct answer: 900 kg m/s Review Section 7-3 in Giancoli.
6.	What is the impulse shown in the following figure? The correct answer: 450 Ns You probably only found the area of one of the triangles.
7.	If the impulse is applied to a 200 gm model rocket at rest what will be its final speed? The correct answer: 2250 m/s Review Section 7-3 in Giancoli.
8.	What constant force acting over the same time as the force in question 6 would produce the same impulse? The correct answer: 50 N The time period is nine seconds. Review Figure 7-10 in Giancoli.
9.	If each mass in the figure is 1 kg, what is the x location of the center of mass? The correct answer: 1.0 Review Example 7-11 in Giancoli.
10.	If each mass in the figure is 1 kg, what is the y location of the center of mass? The correct answer: .33 Review Section 7-8 in Giancoli.
11.	If the mass of m1 and m3 in the figure is 1 kg and m2 is 2 kg, what is the x location of the center of mass? The correct answer: 1.0 Review Section 7-8 in Giancoli.
12.	If the mass of m1 and m3 in the figure is 1 kg and m2 is 2 kg, what is the y location of the center of mass? Your answer: .5
13.	If the mass of m1 is 1 kg and m3 is 2 kg in the figure and m2 is 3 kg, what is the x location of the center of mass? The correct answer: 1.17 Review Section 7-8 in Giancoli.
14.	If the mass of m1 is 1 kg and m3 is 2 kg in the figure and m2 is 3 kg, what is the y location of the center of mass?
15.	If all the masses in the figure have a mass of 2 kg, and m2 has speed 2 m/s and m3 has a speed of 4 m/s, what is the x-component of the momentum of the center of mass? The correct answer: 4 kg m/s Review Section 7-10 in Giancoli.
16.	If all the masses in the figure have a mass of 2 kg, and m2 has speed 2 m/s and m3 has a speed of 4 m/s, what is the y-component of the momentum of the center of mass? The correct answer: 8 kg m/s Did you forget that m2 has a mass of 2 kg. Review Section 7-8 in Giancoli.
17.	What is the magnitude of the momentum of the center of mass of the system of particles in question 15? The correct answer: 8.9 kg m/s This is the magnitude of the x component. Review Section 7-10 in Giancoli.
18.	What is the direction of the momentum of the center of mass of the particles in question 15, as measured in degrees counter clockwise from East. Your answer: 63
19.	A 12000 kg railroad car travelling at 10 m/s strikes and couples with a 6000 kg caboose at rest. What is the speed of the final combination? The correct answer: 6.7 m/s This would be true if it were the 6000 kg car that is moving. Review Example 7-3 in Giancoli.
20.	A 12000 kg railroad car travelling at 10 m/s strikes and couples with a 6000 kg caboose at rest. What is the loss of Mechanical Energy in the collision? The correct answer: 200000 J Review Example 7-8 in Giancoli.
21.	A 12000 kg railroad car travelling at 10 m/s strikes and couples with a 6000 kg caboose at rest. What would be the speed of the combination of railroad cars if the caboose was initially rolling towards the other car with a speed of 2 m/s? The correct answer: 6.0 m/s The momentum can not cancel out because they don't have the same magnitude. Review Section 7-2 in Giancoli.
22.	A billiard ball travelling to the right at 6m/s overtakes and strikes an identical ball travelling at 3 m/s. What is the speed of the first ball after the collision? Your answer: 3 m/s
23.	A billiard ball travelling to the right at 6m/s overtakes and strikes an identical ball travelling at 3 m/s. What is the speed of the second ball after the collision? The correct answer: 6 m/s With this answer energy is not conserved. Review Section 7-5 in Giancoli.
24.	A billiard ball travelling to the right at 6m/s overtakes and strikes an identical ball travelling at 3 m/s. What is the speed of the first ball after collision if the second ball was travelling at it (instead of away from it) with a speed of 3 m/s before collision? The correct answer: -3 m/s The momentum of the second ball is negative. Review Section 7-5 in Giancoli.
25.	What is the speed of the second ball in question 24 after collision? The correct answer: 6 m/s The balls can't pass through each other. Review Section 7-5 in Giancoli.