A 2.0 kg cart moves to the right at 3.0 m/s. What is the magnitude of its linear momentum?
6.0 kg m/s
1.5 kg m/s
5.0 kg m/s
0.67 kg m/s
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WhyMomentum p = m*v = 2.0 kg * 3.0 m/s = 6.0 kg m/s.
2Multiple choice · Easy
Which of the following is the correct SI unit for impulse?
N s
N/s
kg m/s^2
J/s
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WhyImpulse equals force times time, so its unit is N s, which is equivalent to kg m/s.
3Multiple choice · Easy
A constant force of 5.0 N acts on an object for 4.0 s. What is the magnitude of the impulse delivered?
20 N s
1.25 N s
9.0 N s
40 N s
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WhyImpulse J = F*t = 5.0 N * 4.0 s = 20 N s.
4Multiple choice · Easy
In a perfectly inelastic collision between two objects, what happens immediately after the collision?
The objects stick together and move with a common velocity
The objects bounce apart with their original speeds
Kinetic energy is conserved
Total momentum is destroyed
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WhyIn a perfectly inelastic collision the objects stick together and move with a common velocity.
5Multiple choice · Easy
Which quantity is always conserved in an isolated system with no external forces?
Total linear momentum
Total kinetic energy only
The velocity of each individual object
The momentum of each individual object
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WhyTotal linear momentum is conserved whenever the net external force on the system is zero.
6Fill in the blank · Easy
The impulse-momentum theorem states that the net impulse on an object equals its change in .
Answer:
momentum / linear momentum
WhyThe net impulse delivered to an object equals the change in its momentum: J = delta p.
7Multiple choice · Medium
A 0.15 kg ball moving at 20 m/s is caught and brought to rest in 0.10 s. What is the average force exerted on the ball?
30 N
3.0 N
300 N
15 N
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Whydelta p = m*delta v = 0.15*(0-20) = -3.0 kg m/s. F = delta p / t = -3.0/0.10 = -30 N, magnitude 30 N.
8Multiple choice · Medium
A 1.0 kg cart at 4.0 m/s collides and sticks to a stationary 3.0 kg cart. What is their common speed after the collision?
1.0 m/s
2.0 m/s
4.0 m/s
0.5 m/s
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WhyConservation of momentum: (1.0*4.0)/(1.0+3.0) = 4.0/4.0 = 1.0 m/s.
9Multiple choice · Medium
A 0.50 kg ball hits a wall at 6.0 m/s and rebounds at 4.0 m/s in the opposite direction. What is the magnitude of the change in its momentum?
5.0 kg m/s
1.0 kg m/s
3.0 kg m/s
10 kg m/s
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WhyTaking initial as +, delta p = m*(vf - vi) = 0.50*(-4.0 - 6.0) = -5.0 kg m/s, magnitude 5.0 kg m/s.
10Multiple choice · Medium
Two equal-mass objects approach each other with equal and opposite momenta and collide head-on. What is the total momentum of the system just after the collision?
Zero
Twice the momentum of one object
Equal to the momentum of the faster object
Cannot be determined without the masses
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WhyThe total momentum before is zero, so by conservation the total momentum after is also zero regardless of collision type.
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