Question 1

Which of the following best describes a force?

Accepted Answer

A vector quantity that measures the interaction between objects.

Question 2

The SI unit of force is the Newton. Which of the following correctly expresses 1 Newton in base SI units?

Accepted Answer

$$1N = 1 \frac{kg \cdot m}{s^2$}$$

Question 3

A block is moving across a horizontal surface with constant velocity. Which statement is true about the forces acting on it?

Accepted Answer

The net force on the block is zero.

Question 4

According to Newton's First Law, what happens to an object at rest if no net external force acts on it?

Accepted Answer

It will remain at rest.

Question 5

Which of the following is an example of a field force?

Accepted Answer

Gravitational force

Question 6

A 0.5 kg object is subject to Earth's gravity ($$g = 9.8 \frac{m}{s^2$}). $$What is the magnitude of the gravitational force acting on it?

Accepted Answer

$$4.9\ N$$

Question 7

A person pulls a rope with a force of $$1000\ N to $$the right, while another person pulls with $$1000\ N to $$the left. What is the tension in the rope (assuming the rope is massless and in equilibrium)?

Accepted Answer

$$1000\ N$$

Question 8

Which of the following statements about Newton's Third Law is correct?

Accepted Answer

The action and reaction forces are equal in magnitude and opposite in direction.

Question 9

A 5 kg block is at rest on a frictionless horizontal surface. A horizontal force of $$20\ N is $$applied to it. What is the acceleration of the block?

Accepted Answer

$$4\ m/s^2$

Question 10

A 325 N bag of cement hangs in equilibrium from three wires. If two wires make angles $$\$$theta_1$$ = 60^\circ$$ and $$\$$theta_2$$ = 40^\circ$$ with the horizontal, and the system is in equilibrium, which of the following is true about the sum of the vertical components of the tensions?

Accepted Answer

The sum is equal to 325 N.

Question 11

A block of mass $$m is on an $$incline at angle $$	heta. $$What is the component of the gravitational force acting parallel to the incline?

Accepted Answer

$$mg \sin 	heta$$

Question 12

A 2 kg block and a 3 kg block are pushed together on a frictionless surface by a force of $$20\ N. $$What is the force that the 2 kg block exerts on the 3 kg block?

Accepted Answer

$$12\ N$$

Question 13

Which of the following best describes the normal force acting on an object resting on a horizontal surface?

Accepted Answer

It is the reaction force exerted by the surface, perpendicular to the surface.

Question 14

A block slides down a frictionless incline of length $$5.0\ m at an $$angle of $$15^\circ. $$What is the acceleration of the block?

Accepted Answer

$$2.54\ m/s^2$

Question 15

Nellie Newton stands motionless on a weighing scale on a horizontal surface. The reading is $$mg. $$When she stands on an incline, the scale reads:

Accepted Answer

Less than $$mg$$

Question 16

Which of the following is NOT a contact force?

Accepted Answer

Gravitational force

Question 17

If the net force acting on an object is zero, which of the following must be true?

Accepted Answer

The object is moving at constant velocity or at rest.

Question 18

A block of mass $$m is $$suspended by a rope. If the block is at rest, what is the tension $$T in $$the rope?

Accepted Answer

$$T = mg$$

Question 19

Which of the following statements about mass is correct?

Accepted Answer

Mass is a measure of the amount of matter and is a scalar.

Question 20

A block is at rest on a frictionless surface. Which law explains why it remains at rest?

Accepted Answer

Newton's First Law

Physics 111: Chapter 4 – Laws of Motion (Study Notes)

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