# Exam 3 Quiz 2

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• 1.

### An action exerted on an object which may change the object’s state of rest or motion defines

• A.

Acceleration

• B.

Force

• C.

Mass

• D.

Velocity

B. Force
Explanation
Force is defined as an action exerted on an object that has the potential to change the object's state of rest or motion. It can cause an object to start moving, stop moving, or change its direction and speed. Force is a vector quantity, meaning it has both magnitude and direction. It is measured in units of Newtons (N).

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• 2.

### Which of the following statements are true about the concept of field forces?I.   Field forces can be exerted by objects that are in physical contact.II. Field forces can be exerted by objects that are not in contact.III. There are four fundamental field forces.

• A.

I only

• B.

II only

• C.

II and III

• D.

I, II, and III

C. II and III
Explanation
Field forces can be exerted by objects that are not in contact, which means that objects can influence each other without physical contact. This is true for gravitational forces, electromagnetic forces, and nuclear forces. Additionally, there are indeed four fundamental field forces: gravitational force, electromagnetic force, strong nuclear force, and weak nuclear force. Therefore, the correct answer is II and III.

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• 3.

### Two pumpkins are sitting next to each other on Ms. Overby’s front porch. The force due to gravity on the first pumpkin is 9 N and on the second is 13 N. The gravitational force on the porch itself is 125 N. The ground supports the porch with an upward force of 147 N. In a free-body diagram of the porch, how many contact forces and how many field forces should be represented?

• A.

1, 2

• B.

1, 3

• C.

2, 2

• D.

3, 1

D. 3, 1
Explanation
In a free-body diagram of the porch, there should be three contact forces represented because the porch is in contact with the ground, the first pumpkin, and the second pumpkin. There should also be one field force represented, which is the gravitational force acting on the porch due to gravity.

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• 4.

### Which of the following situations describes inertia?

• A.

A stationary object tends to resist being moved.

• B.

A moving object tends to resist a change in speed.

• C.

A moving object tends to resist a change in direction.

• D.

All of the above

D. All of the above
Explanation
The correct answer is "all of the above" because inertia is the tendency of an object to resist changes in its state of motion. This includes resisting being moved when stationary, resisting a change in speed when already moving, and resisting a change in direction. In each situation, the object's inertia is causing it to resist any change to its current state of motion.

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• 5.

### Which of the following is true of inertia?

• A.

It is described in Newton’s first law of motion.

• B.

It is a property of motion.

• C.

It is measured by weight.

• D.

All of the above

A. It is described in Newton’s first law of motion.
Explanation
The correct answer is "It is described in Newton’s first law of motion." This is because inertia is defined as the tendency of an object to resist changes in its motion. Newton's first law of motion states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and direction, unless acted upon by an external force. Therefore, inertia is directly related to the first law of motion. The other options, "It is a property of motion" and "It is measured by weight," are not true statements about inertia.

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• 6.

### An object is at rest on an incline. The component of gravity acting downward below the incline on the object is described as Fg= 8.0 N. Which axis is pointing up along the incline?

• A.

+ x-axis

• B.

+ y-axis

• C.

- x-axis

• D.

- y-axis

C. - x-axis
Explanation
The component of gravity acting downward below the incline is described as Fg= 8.0 N. Since the component of gravity is acting downward, it opposes the upward direction. Therefore, the axis pointing up along the incline would be the negative x-axis.

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• 7.

### Which of the following statements describe an object in equilibrium?I.   The object is at rest.II.  The object is moving at constant velocity.III. The net external force on the object is zero.

• A.

I and II

• B.

I and III

• C.

II and III

• D.

I, II, and III

D. I, II, and III
Explanation
An object is in equilibrium when it is at rest (statement I) or moving at a constant velocity (statement II). In both cases, the object's acceleration is zero, meaning there is no change in its motion. Additionally, for an object to be in equilibrium, the net external force acting on it must be zero (statement III). This means that the forces acting on the object are balanced and cancel each other out, resulting in no acceleration. Therefore, all three statements accurately describe an object in equilibrium.

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• 8.

### A rigid rod holds a Witch’s broom shop sign horizontally from the side of a building. The force due to gravity acting on the sign is 165 N with the angle between the sign and the rod being 50.0. Ignoring the weight of the rod, what is the magnitude of the tension in the rod?

• A.

215 N

• B.

165 N

• C.

126 N

• D.

257 N

A. 215 N
Explanation
The magnitude of the tension in the rod is 215 N. This can be determined by considering the forces acting on the sign. Since the sign is held horizontally, the tension in the rod must balance out the force due to gravity acting on the sign. The force due to gravity is 165 N, and since the angle between the sign and the rod is given as 50.0 degrees, we can use trigonometry to calculate the tension in the rod. By using the cosine function, we can find that the tension is equal to the force due to gravity divided by the cosine of the angle. Therefore, the tension in the rod is 165 N / cos(50.0) = 215 N.

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• 9.

### A goblin is holding a skull above his head with a mass of 353 kg. The goblin’s mass is 193 kg. Draw a free-body diagram showing the various forces in the problem. Calculate the normal force exerted on each of the goblin’s feet during the time he was holding the skull.

• A.

5356 N

• B.

5460 N

• C.

2678 N

• D.

2730 N

C. 2678 N
Explanation
The normal force exerted on each of the goblin's feet can be calculated using Newton's second law, which states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration. In this case, the goblin is holding the skull above his head, so there is an upward force of 353 kg * 9.8 m/s^2 (gravitational acceleration) acting on the skull. According to Newton's third law, there is an equal and opposite force acting on the goblin's feet, which is the normal force. Since the goblin's mass is 193 kg, the normal force exerted on each of his feet is (353 kg * 9.8 m/s^2) / 2 = 2678 N.

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• 10.

### The net force exerted by a bat’s wing when it flies can be as large as 7.90 N, assuming that the bat has a mass of 60.0 g. Assume that two different muscles pull the bat’s wing forward and downward, exerting a net force of 7.90 N. If the forces exerted by the muscles are at right angles to each other and the muscle that pulls the bat’s wing downward exerts a force of 1.30 N, what is the magnitude of the force exerted by the other muscle? Draw a free-body diagram showing the forces acting on the bat’s wing.

• A.

60.7 N

• B.

7.8 N

• C.

8.0 N

• D.

64.1 N

B. 7.8 N
Explanation
The magnitude of the force exerted by the other muscle can be found using the Pythagorean theorem. Since the forces exerted by the muscles are at right angles to each other, we can treat them as the two legs of a right triangle. The force pulling the bat's wing downward is one leg with a magnitude of 1.30 N, and the net force exerted by both muscles is the hypotenuse with a magnitude of 7.90 N. Using the Pythagorean theorem, we can calculate the magnitude of the other force as √(7.90^2 - 1.30^2) = 7.8 N. Therefore, the magnitude of the force exerted by the other muscle is 7.8 N.

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• Mar 16, 2023
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• Oct 30, 2014
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