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The value of the momentum of a system is the same at a later time as at an earlier time if there are no _____ . Se

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## The value of the momentum of a system is the same at a later time as at an earlier time if there are no _____ . Se

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**The value of the momentum of a system is the same at a later**time as at an earlier time if there are no _____ . Select the correct answer. • collisions between particles within the system • inelastic collisions between particles within the system • changes of momentum of individual particles within the system • internal forces acting between particles within the system • external forces acting on particles of the system**Two bodies with masses m1 and m2 are both moving east with**velocities of magnitudes v1 and v2, where v1 is less than v2. The magnitude of the velocity of this two-body system's center of mass is _____ . Select the correct answer. • less than v1 • equal to v1 • equal to the average of v1 and v2 • greater than v1 and less than v2 • greater than v2**A rocket with an initial mass of 1500 kg adjusts its thrust**by varying the rate at which mass is ejected. The ejection speed relative to the rocket is 40 km/s. If the acceleration of the rocket is to have a magnitude of 20 m/s2 at an instant when its mass is 80% of the original mass, at what rate is mass being ejected at that instant? Ignore any external forces on the rocket. Select the correct answer. • 0.60 kg/s • 0.70 kg/s • 0.40 kg/s • 0.30 kg/s • 0.20 kg/s**A 3.0-kg object moving in the positive x direction has a**one-dimensional elastic collision with a 9.0-kg object initially at rest. After the collision the 9.0-kg object has a velocity of 2.0 m/s in the positive x direction. What was the initial speed of the 3.0 kg object? Select the correct answer. • 4.0 m/s • 3.6 m/s • 4.8 m/s • 2.8 m/s • 2.4 m/s**If you know the impulse that has acted on a body of mass m**you can calculate _____ . Select the correct answer. • its initial velocity • its final velocity • its final momentum • the change in its velocity • its acceleration during the impulse**A 6.0-kg object moving 2.0 m/s in the positive x direction**has a one-dimensional elastic collision with a 4.0-kg object moving 4.0 m/s in the opposite direction. What is the total kinetic energy of the two-mass system after the collision? Select the correct answer. • 44 J • 48 J • 35 J • 57 J • 26 J**A 3.0-kg object moving with a speed of 4.7 m/s collides**perpendicularly with a wall and emerges with a speed of 3.0 m/s in the opposite direction. If the object is in contact with the wall for 3.1 m/s, what is the magnitude of the average force on the object by the wall? Select the correct answer. • 7.4 kN • 8.1 kN • 8.9 kN • 9.6 kN • 1.1 kN**A 7.0-kg object moving 5.0 m/s strikes a 5.0-kg object**initially at rest. Immediately after the collision, the 7.0-kg object has a velocity of 3.0 m/s directed 60° from its initial direction of motion. What is the x-component of the velocity of the 5.0-kg object just after the collision? Select the correct answer. • 4.9 m/s • 5.9 m/s • 6.9 m/s • 7.8 m/s • 8.8 m/s**An 6.0-kg object moving 7.0 m/s in the positive x direction**has a one-dimensional collision with a 4.0-kg object moving 3.0 m/s in the opposite direction. The final velocity of the 6.0-kg object is 2.0 m/s in the positive x direction. What is the total kinetic energy of the two-mass system after the collision? Select the correct answer. • 53 J • 42 J • 32 J • 85 J • 95 J**A 3.00 kg stone is dropped from a 26.1 m high building. When**the stone has fallen 19.6 m, the magnitude of the impulse it has received from the gravitational force is _____ . Select the correct answer. • 9.8 N·s • 19.6 N·s • 29.4 N·s • 58.8 N·s • 117.6 N·s**A 2.0-kg object moving 8.0 m/s collides with and sticks to**an 6.0-kg object initially at rest. Determine the kinetic energy lost by the system as a result of this collision. Select the correct answer. • 48 J • 58 J • 29 J • 19 J • 6.0 J