Quiz 6: Linear Momentum

1.

If a mass is at rest, what must be applied to cause it to move?

A.

Kilograms
B.

Speed
C.

Vectors
D.

Force

Correct Answer
D. Force

Explanation
To cause a mass at rest to move, a force must be applied. Force is a push or pull that can change the motion of an object. In this case, the force applied will overcome the inertia of the mass and initiate its movement. Without the application of force, the mass will remain at rest according to Newton's first law of motion.

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2.

A person jumps to the ground from a platform 10 feet high. Which of the following is true?

A.

The person has more kinetic energy before they jump than after they jump.
B.

The person has less potential energy at the top of the platform than in the air.
C.

The person's potential energy at the instant they jump is approximately equal to their kinetic energy the instant they land.
D.

The person's kinetic energy at the instant they jump is approximately double their potential energy the instant they land.

Correct Answer
C. The person's potential energy at the instant they jump is approximately equal to their kinetic energy the instant they land.

Explanation
When the person jumps from the platform, they lose potential energy due to the decrease in height. This potential energy is converted into kinetic energy as the person falls. At the instant they jump, their potential energy is equal to their kinetic energy at the instant they land. This is because energy is conserved in the system, and the potential energy lost is equal to the kinetic energy gained.

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3.

The kinetic energy of an object will increase the most if you __________________.

A.

Double the velocity of the object
B.

Double the mass of the object
C.

Double the potential energy
D.

Double the temperature of the object

Correct Answer
A. Double the velocity of the object

Explanation
The kinetic energy of an object is directly proportional to its velocity squared. Therefore, if you double the velocity of the object, the kinetic energy will increase the most.

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4.

An object with mass "m" kilograms is suspended "h" meters above the ground by a string. If the string is cut, what will the velocity of the object be at the instant it hits the ground?

A.

The square root of 2gh
B.

One-half the mass squared
C.

Two times ghm squared
D.

H-2gm

Correct Answer
A. The square root of 2gh

Explanation
When the object is dropped, it will accelerate due to gravity. The velocity of the object at the instant it hits the ground can be determined using the equation for the velocity of an object in free fall. This equation is given by v = sqrt(2gh), where "v" is the velocity, "g" is the acceleration due to gravity, and "h" is the height from which the object is dropped. Therefore, the correct answer is the square root of 2gh.

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5.

Which of the following is NOT a consequence of "The Law of Conservation of Energy"?

A.

Potential Energy can never be greater than Kinetic Energy
B.

The energy in a closed system is always constant
C.

The Kinetic Energy of a dropped object at the instant it hits the ground is roughly equal to the potential energy of the object at the instant it was dropped
D.

It is not necessary to use Kinematics to discover the velocity of an object accelerated by gravity if you know it's initial Potential Energy and its mass.

Correct Answer
A. Potential Energy can never be greater than Kinetic Energy

Explanation
The Law of Conservation of Energy states that energy cannot be created or destroyed, only transferred or transformed from one form to another. This means that the total energy in a closed system remains constant. The statement "Potential Energy can never be greater than Kinetic Energy" is not a consequence of this law because potential energy can indeed be greater than kinetic energy. For example, when an object is at its highest point in a vertical motion, it has maximum potential energy and zero kinetic energy. As it falls, its potential energy decreases while its kinetic energy increases. Therefore, the given statement is not a consequence of the Law of Conservation of Energy.

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6.

Momentum is the product of ___________.

A.

Mass times velocity
B.

Force times distance
C.

Speed times acceleration
D.

Time and space

Correct Answer
A. Mass times velocity

Explanation
Momentum is defined as the product of an object's mass and its velocity. Mass refers to the amount of matter an object contains, while velocity is the speed of an object in a given direction. When these two quantities are multiplied together, we get the momentum of the object. Therefore, the correct answer is "mass times velocity."

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7.

If two objects collide with each other, _______________.

A.

The sum of their momentums after the collision is equal to the sum of their momentums before the collision
B.

The momentum before the collision is always greater than the total momentum after the collision
C.

The object with greater mass always has greater momentum
D.

They both lose momentum at the moment of impact

Correct Answer
A. The sum of their momentums after the collision is equal to the sum of their momentums before the collision

Explanation
When two objects collide with each other, the law of conservation of momentum states that the total momentum before the collision is equal to the total momentum after the collision. This means that the sum of their momentums after the collision is equal to the sum of their momentums before the collision. This principle holds true regardless of the masses of the objects involved.

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8.

If a football player running down the field is tackled by another football player who holds onto the first football player so that they both fly out of bounds together, that collision is ___________.

A.

Elastic
B.

Inelastic
C.

Momentum
D.

Invisible

Correct Answer
B. Inelastic

Explanation
When the two football players collide and fly out of bounds together, it suggests that there is a loss of kinetic energy in the collision. This loss of energy indicates that the collision is inelastic. In an inelastic collision, the objects stick together or deform upon impact, resulting in a decrease in kinetic energy.

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9.

When playing billiards, the collisions between the balls are best described as __________________.

A.

Elastic
B.

Inelastic
C.

Expensive
D.

Exhaustive

Correct Answer
A. Elastic

Explanation
The collisions between the balls in billiards are best described as elastic because in an elastic collision, the total kinetic energy of the system is conserved. This means that when two balls collide, they bounce off each other without any loss of energy. In billiards, this is desirable as it allows for accurate and predictable ball movements, making the game more enjoyable and fair.

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10.

Momentum is a __________ measurement.

A.

Vector
B.

Scalar
C.

Negative
D.

Quantitative

Correct Answer
A. Vector

Explanation
Momentum is a vector measurement because it has both magnitude and direction. In physics, momentum is defined as the product of an object's mass and velocity. Since velocity is a vector quantity, with both magnitude (speed) and direction, momentum inherits these properties. This means that momentum not only tells us how fast an object is moving, but also in which direction it is moving. Therefore, momentum is considered a vector measurement.

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