Exam 3 Quiz #5

1.

The length of a force vector represents the

A.

Cause of the force
B.

Direction of the force
C.

Magnitude of the force
D.

Type of force

Correct Answer
C. Magnitude of the force

Explanation
The length of a force vector represents the magnitude of the force. In physics, the magnitude of a force refers to the strength or intensity of the force. It is a scalar quantity that is represented by the numerical value of the force. The length of a force vector is directly proportional to the magnitude of the force it represents. Therefore, by measuring the length of the vector, one can determine the magnitude of the force.

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2.

A free-body diagram represents all of the following except

A.

The object
B.

Forces as vectors
C.

Forces exerted by the object
D.

Forces exerted on the object

Correct Answer
C. Forces exerted by the object

Explanation
A free-body diagram represents the forces exerted on the object, not the forces exerted by the object itself. It is a visual representation that shows all the external forces acting on an object, such as gravitational forces, normal forces, frictional forces, and applied forces. The diagram helps to analyze and understand the motion of the object by considering the net force acting on it.

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3.

In the free-body diagram shown to the right, which of the following is the normal force acting on the car?

A.

5800 N
B.

14,700 N
C.

775 N
D.

13, 690 N

Correct Answer
D. 13, 690 N

Explanation
The normal force is the force exerted by a surface to support the weight of an object resting on it. In this case, the normal force acting on the car can be determined by balancing the weight of the car. Since the weight of the car is equal to its mass multiplied by the acceleration due to gravity, and the mass and gravity are constant, the normal force must also be constant. Therefore, the correct answer is 13,690 N.

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4.

A car goes forward along a level road at constant velocity. The additional force needed to bring the car into equilibrium is

A.

Greater than the normal force times the coefficient of static friction.
B.

Equal to the normal force times the coefficient of static friction.
C.

The normal force times the coefficient of kinetic friction.
D.

Zero

Correct Answer
D. Zero

Explanation
When a car is moving forward along a level road at a constant velocity, it means that the forces acting on the car are balanced. In this situation, the additional force needed to bring the car into equilibrium is zero. This is because the car is already in equilibrium, so no additional force is required.

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5.

A small force acting on a human-sized object causes

A.

A small acceleration
B.

A large acceleration
C.

No acceleration
D.

Equilibrium

Correct Answer
A. A small acceleration

Explanation
When a small force is applied to a human-sized object, it causes a small acceleration. This is because acceleration is directly proportional to the force applied, according to Newton's second law of motion. Therefore, a small force will result in a small acceleration, while a larger force would cause a larger acceleration.

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6.

Two forces act on an object. The magnitude of the net force acting on the object

A.

Equals the sum of the magnitudes of the two forces.
B.

Equals the difference in the magnitudes of the two forces.
C.

Equals the average of the two forces.
D.

Cannot be determined from the given information.

Correct Answer
A. Equals the sum of the magnitudes of the two forces.

Explanation
When two forces act on an object, the net force is the vector sum of the individual forces. Since the question states that the magnitude of the net force is being asked, we only need to consider the magnitudes of the forces. Therefore, the correct answer is that the magnitude of the net force equals the sum of the magnitudes of the two forces.

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7.

A newton is equivalent to which of the following quantities?

A.

Kg
B.

Kg•m/s^2
C.

Kg•m/s
D.

Kg•(m/s)^2

Correct Answer
B. Kg•m/s^2

Explanation
A newton is equivalent to kg•m/s^2. This is because a newton is the unit of force in the International System of Units (SI), and force is defined as the product of mass and acceleration. In SI units, mass is measured in kilograms (kg) and acceleration is measured in meters per second squared (m/s^2). Therefore, the correct answer is kg•m/s^2.

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8.

If a nonzero net force is acting on an object, then the object is definitely

A.

At rest
B.

Being accelerated
C.

Moving with constant velocity
D.

Losing mass

Correct Answer
B. Being accelerated

Explanation
If a nonzero net force is acting on an object, it means that there is an unbalanced force acting on the object. According to Newton's second law of motion, an unbalanced force will cause the object to accelerate. Therefore, the correct answer is "being accelerated".

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9.

A cabinet initially at rest on a horizontal surface requires a 115 N horizontal force to set it in motion. If the coefficient of static friction between the cabinet and the floor is 0.38, what is the normal force exerted on the cabinet?

A.

303 N
B.

44 N
C.

12 N
D.

1128 N

Correct Answer
A. 303 N

Explanation
The normal force exerted on the cabinet is 303 N. The normal force is the force exerted by a surface to support the weight of an object resting on it. In this case, the normal force is equal to the weight of the cabinet. Since the cabinet is initially at rest, the force required to set it in motion is equal to the maximum static friction force. The maximum static friction force can be calculated by multiplying the coefficient of static friction by the normal force. In this case, the maximum static friction force is 0.38 times the normal force. Setting this equal to 115 N and solving for the normal force gives a value of 303 N.

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10.

A 20.0 kg trunk is pushed across the floor of a moving van by a horizontal force. If the coefficient of kinetic friction between the trunk and the floor is 0.255, what is the magnitude of the frictional force acting on the trunk?

A.

3 N
B.

769 N
C.

196 N
D.

50 N

Correct Answer
D. 50 N

Explanation
The magnitude of the frictional force acting on the trunk can be found using the formula: frictional force = coefficient of friction x normal force. The normal force is equal to the weight of the trunk, which is mass x acceleration due to gravity. Therefore, the normal force is 20.0 kg x 9.8 m/s^2 = 196 N. Plugging this value into the formula, we get: frictional force = 0.255 x 196 N = 50 N.

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11.

A passenger with a mass of 60.0 kg is standing in a subway car that is accelerating at 3.70 m/s². If the coefficient of static friction between the passenger’s shoes and the car floor is 0.455, will the passenger be able to stand without sliding? Prove your answer.

A.

Yes; Fs= 268 N and Fa= 222 N
B.

No; Fs= 268 N and Fa= 222 N
C.

Yes; Fs= 222 N and Fa= 268 N
D.

No; Fs= 222 N and Fa = 268 N

Correct Answer
A. Yes; Fs= 268 N and Fa= 222 N

Explanation
The coefficient of static friction (Fs) can be calculated by multiplying the mass of the passenger (60.0 kg) by the acceleration due to gravity (9.8 m/s^2) and the coefficient of static friction (0.455). Fs = 60.0 kg * 9.8 m/s^2 * 0.455 = 268 N. The force of acceleration (Fa) can be calculated by multiplying the mass of the passenger (60.0 kg) by the acceleration of the subway car (3.70 m/s^2). Fa = 60.0 kg * 3.70 m/s^2 = 222 N. Since Fs (268 N) is greater than Fa (222 N), the static friction force is greater than the force of acceleration, meaning the passenger will be able to stand without sliding.

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12.

A 90.0 kg skier glides down a slope with an incline of 17.0°. What frictional force is needed for the skier to move at a constant velocity?

A.

883 N
B.

258 N
C.

844 N
D.

323 N

Correct Answer
B. 258 N

Explanation
The skier is moving at a constant velocity, which means there is no net force acting on them. The only force opposing their motion is the force of friction. According to Newton's second law, the force of friction can be calculated using the equation F = μN, where μ is the coefficient of friction and N is the normal force. In this case, since the skier is on an incline, the normal force is equal to the weight of the skier, which is mg, where m is the mass of the skier and g is the acceleration due to gravity. Therefore, the frictional force needed for the skier to move at a constant velocity is equal to μmg. Since the mass of the skier is 90.0 kg and the acceleration due to gravity is 9.8 m/s^2, the frictional force is 90.0 kg * 9.8 m/s^2 = 882 N. The closest answer choice to this is 883 N.

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Exam 3 Quiz #5

The length of a force vector represents the

A free-body diagram represents all of the following except

In the free-body diagram shown to the right, which of the following is the normal force acting on the car?

A car goes forward along a level road at constant velocity. The additional force needed to bring the car into equilibrium is

A small force acting on a human-sized object causes

Two forces act on an object. The magnitude of the net force acting on the object

A newton is equivalent to which of the following quantities?

If a nonzero net force is acting on an object, then the object is definitely

A cabinet initially at rest on a horizontal surface requires a 115 N horizontal force to set it in motion. If the coefficient of static friction between the cabinet and the floor is 0.38, what is the normal force exerted on the cabinet?

A 20.0 kg trunk is pushed across the floor of a moving van by a horizontal force. If the coefficient of kinetic friction between the trunk and the floor is 0.255, what is the magnitude of the frictional force acting on the trunk?

A passenger with a mass of 60.0 kg is standing in a subway car that is accelerating at 3.70 m/s2. If the coefficient of static friction between the passenger’s shoes and the car floor is 0.455, will the passenger be able to stand without sliding? Prove your answer.

A 90.0 kg skier glides down a slope with an incline of 17.0°. What frictional force is needed for the skier to move at a constant velocity?

A passenger with a mass of 60.0 kg is standing in a subway car that is accelerating at 3.70 m/s². If the coefficient of static friction between the passenger’s shoes and the car floor is 0.455, will the passenger be able to stand without sliding? Prove your answer.