Question 1

A 1000-kg car is driving toward the north along a straight road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest in a distance of 140 m. What is the constant force applied to the car to bring it to rest? A)1.43 N north B)7.00 × 10³ N south C)1.43 × 10³ N south D)1.43 N south E)143 N south

Accepted Answer

The work-energy principle states that the work done by the brakes is equal to the change in kinetic energy. The initial kinetic energy is (1/2)mv² = (1/2)(1000 kg)(20 m/s)² = 200,000 J. The work done is force × distance, so force = work/distance = 200,000 J / 140 m = 1,428.57 N, approximately 1.43 × 10³ N south.

Question 2

FIGURE 4-8 
-The three forces represented in Fig. 4-8 act on an object. What fourth force must act on the object so that the object does not accelerate?
A)7.0 N  + 2.0 N

B)1.0 N  - 5.0 N

C)3.0 N  + 4.0 N

D)-1.0 N  + 5.0 N

E)3.0 N  - 4.0 N

Accepted Answer

The answer of FIGURE 4-8 
-The three forces represented in...

Question 3

A 2.00-kg object moves with constant velocity 3.00 m/s toward the east. Two forces act on the object. The first is a 40.0 N force toward the west. What is the second force that acts on the object?
A)23.0 N east
B)40.0 N east
C)26.7 N east
D)46.0 N east
E)46.0 N west

Accepted Answer

Since the object moves with constant velocity, the net force acting on it must be zero. Therefore, the second force must be equal in magnitude and opposite in direction to the first force (40.0 N west), which means it is 40.0 N east.

Question 4

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0-kg, 3.0-kg, and 2.0-kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two masses.
(a) Draw the free-body diagrams for each of the masses.
(b) What is the contact force between the 5.0-kg mass and the 3.0-kg mass?
(c) What is the contact force between the 3.0-kg and the 2.0-kg mass?

Accepted Answer

The answer of Three boxes rest side-by-side on a smooth,...

Question 5

Two objects push on each other. The first object has a mass 30.0 kg and it accelerates at 2.00 m/s² toward the east. The second object has a mass 7.00 kg. If no other forces are acting on the objects, what is the acceleration of the second object? A)4.67 m/s² west B)1.14 m/s² east C)2.00 m/s² west D)8.57 m/s² west E)4.67 m/s² east

Accepted Answer

The answer of Two objects push on each other. The...

Question 6

Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s in 2.0 s. What is the net force acting on the body?
A)2.0 N
B)4.0 N
C)8.0 N
D)16 N
E)32 N

Accepted Answer

F = ma = (4.0 kg)(8.0 m/s) / (2.0 s) = 16 N

Question 7

Object A is acted on by only object B. The mass of object A is 20.0 kg and its acceleration is 4.00 m/s² west. Object B is acted on by two forces, the force of object A on object B and another unknown force. If mass of object B is 40.0 kg and the acceleration of object B is 3.00 m/s² west, what is the unknown force? A)40 N west B)120 N west C)80 N east D)200 N west E)80 N west

Accepted Answer

The answer of Object A is acted on by only...

Question 8

FIGURE 4-10 
-The three forces represented in Fig. 4-10 act on an object. What is the direction of the acceleration of the object?
A)11.3° clockwise from the -x-axis
B)11.3° counterclockwise from the +y-axis
C)78.7° counterclockwise from the +x-axis
D)11.3° clockwise from the +y-axis
E)The mass of the object must be known to answer the question.

Accepted Answer

The direction of acceleration is determined by the net force vector, which is the vector sum of the three forces. The angle given (11.3° counterclockwise from the +y-axis) indicates the direction of this net force. The mass of the object is not needed to determine the direction, only the magnitude of acceleration.

Question 9

Two forces act on a 4.00-kg object in a manner that the object has an acceleration 3.00 m/s² in a direction 20.0° north of east. The first force is 15.00 N in a direction 10.0° west of north. What is the second force? A)14.6 N in a direction 28.1° south of east B)12.9 N in a direction 28.1° south of east C)16.2 N in a direction 30.2° south of east D)18.8 N in a direction 41.1° south of east E)17.5 N in a direction 37.5° south of east

Accepted Answer

The answer of Two forces act on a 4.00-kg object...

Question 10

The following four forces act on a 4.00 kg object: F₁ = 300 N east F₂ = 700 N north F₃ = 500 N west F₄ = 600 N south What is the acceleration of the object? A)224 N in a direction 63.4° north of west B)300 N in a direction 63.4° north of west C)300 N in a direction 26.6° north of west D)224 N in a direction 26.6° north of west E)2100 N in a direction 26.6° north of west

Accepted Answer

We need to find the net force acting on the object and then use Newton's second law (F=ma) to find the acceleration. To find the net force, we need to add up all the individual forces taking into account their directions: Fnet = F₁ + F₂ + F₃ + F₄ Fnet = (300 N east) + (700 N north) + (-500 N west) + (-600 N south) Fnet = -100 N south + 200 N east To find the magnitude and direction of the net force, we can use the Pythagorean theorem and trigonometry. Magnitude: |Fnet| = sqrt((-100 N)^2 + (200 N)^2) = 224 N Direction: tan(theta) = opposite/adjacent = (-100 N)/200 N = -0.5 theta = tan^-1(-0.5) = -26.6° (measured counterclockwise from the positive x-axis) However, the question asks for the direction with respect to north of west, which is 90 - theta: 90° - (-26.6°) = 116.6° north of west We can also express this as 63.4° west of north. Therefore, the correct answer is D) 224 N in a direction 26.6° north of west.

Question 11

A person has a mass of 45 kg. How much does she weigh on the Moon, where g = 1.62 m/ s²? A)45 N B)73 N C)7.4 N D)220 N E)440 N

Accepted Answer

The answer of A person has a mass of 45...

Question 12

An astronaut weighs 99.0 N on the Moon, where the acceleration of gravity is 1.62 m/ s². How much does she weigh on Earth? A)16.2 N B)61.0 N C)99.0 N D)600 N E)440 N

Accepted Answer

The answer of An astronaut weighs 99.0 N on the...

Question 13

FIGURE 4-11 
-The free-body diagram of an 8.00 kg object is shown in Fig. 4-11. What is Newton's Second Law for this object?
A)(6.0 N sin 28° - 5.0 N sin 22°)  + (6.0 N cos 28° + 5.0 N cos 22°)  = (8.00 kg) 
B)(6.0 N cos 28° + 5.0 N cos 22°)  + (6.0 N sin 28° + 5.0 N sin 22°)  = (8.00 kg) 
C)(6.0 N cos 28° - 5.0 N sin 22°)  + (6.0 N sin 28° + 5.0 N cos 22°)  = (8.00 kg) 
D)(6.0 N cos 28° - 5.0 N cos 22°)  + (6.0 N sin 28° + 5.0 N sin 22°)  = (8.00 kg) 
E)(6.0 N cos 28° + 5.0 N sin 22°)  + (6.0 N sin 28° - 5.0 N cos 22°)  = (8.00 kg)

Accepted Answer

The answer of FIGURE 4-11 
-The free-body diagram of an...

Question 14

A 1.0-kg object is moving with a constant velocity 2.0 m/s toward the north. There are two forces acting on the object. One of the forces is 2.0 N north. The other force is ________
A)1.0 N north.
B)3.0 N north.
C)2.0 N south.
D)2.0 N north.
E)0.

Accepted Answer

For the object to move with constant velocity, the net force must be zero. Since one force is 2.0 N north, the other force must be 2.0 N south to balance it out.

Question 15

A 1200-kg car starts from rest and accelerates with constant acceleration, traveling 200 m in 9.00 s. What is the force of the road on the car during this acceleration?
A)1.43 kN
B)3.87 kN
C)5.93 kN
D)4.82 kN
E)11.8 kN

Accepted Answer

The answer of A 1200-kg car starts from rest and...

Question 16

The International Space Station has a mass 1.8 × 10⁵ kg. A 70.0-kg astronaut inside the station pushes off one wall of the station so she accelerates at 1.50 m/s². What is the magnitude of the acceleration of the space station as the astronaut is pushing off the wall relative to an observer initially at rest relative to the space station before the push? A)5.8 × 10^-⁴ m/s² B)1.50 m/s² C)4.7 × 10^-⁴ m/s² D)zero E)3.9 × 10^-³ m/s²

Accepted Answer

The astronaut and the space station are pushing on each other with equal and opposite forces. By Newton's third law, the acceleration of the space station is equal in magnitude but opposite in direction to the acceleration of the astronaut. The mass of the space station is much greater than the mass of the astronaut, so the acceleration of the space station is much smaller than the acceleration of the astronaut.

Question 17

A 5.00-kg object is initially at rest. The object is acted on by a 9.00-N force toward the east for 3.00 s. No force acts on the object for the next 4.00 s. How far has the object moved during this 7.00 s interval?
A)8.10 m
B)29.7 m
C)53.6 m
D)21.7 m
E)16.2 m

Accepted Answer

The answer of A 5.00-kg object is initially at rest....

Question 18

FIGURE 4-9 -The two forces indicated in Fig. 4-9 act on a 3.00-kg object. What is the acceleration of the object? A)(1.67 m/s²) - (0.333 m/s²) B)(5.00 m/s²) + (1.00 m/s²) C)(1.67 m/s²) + (2.333 m/s²) D)(15.0 m/s²) + (3.00 m/s²) E)(1.67 m/s²) + (0.333 m/s²)

Accepted Answer

The answer of FIGURE 4-9 
-The two forces indicated in...

Question 19

A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/ s² toward the east? A)6.0 N east B)3.0 N west C)12.0 N east D)9.0 N west E)7.0 N west

Accepted Answer

The answer of A 7.0-kg object is acted on by...

Question 20

A force of 120 N is applied to an object whose mass is 30 kg. The object's acceleration is A)3600 m/ s². B)150 m/ s². C)4.0 m/ s². D)2.0 m/ s². E)0.25 m/ s².

Accepted Answer

Using the formula F=ma where F is the force, m is the mass, and a is the acceleration, we can rearrange to solve for a:
a = F/m
Plugging in the given values, we get:
a = 120 N / 30 kg
a = 4.0 m/s²
Therefore, the object's acceleration is 4.0 m/s².

Quiz 4: Dynamics: Newtons Laws of Motion

A 1000-kg car is driving toward the north along a straight road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest in a distance of 140 m. What is the constant force applied to the car to bring it to rest?

FIGURE 4-8 -The three forces represented in Fig. 4-8 act on an object. What fourth force must act on the object so that the object does not accelerate?

A 2.00-kg object moves with constant velocity 3.00 m/s toward the east. Two forces act on the object. The first is a 40.0 N force toward the west. What is the second force that acts on the object?

Two objects push on each other. The first object has a mass 30.0 kg and it accelerates at 2.00 m/s2 toward the east. The second object has a mass 7.00 kg. If no other forces are acting on the objects, what is the acceleration of the second object?

Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s in 2.0 s. What is the net force acting on the body?

FIGURE 4-10 -The three forces represented in Fig. 4-10 act on an object. What is the direction of the acceleration of the object?

Two forces act on a 4.00-kg object in a manner that the object has an acceleration 3.00 m/s2 in a direction 20.0° north of east. The first force is 15.00 N in a direction 10.0° west of north. What is the second force?

The following four forces act on a 4.00 kg object: F1 = 300 N east F2 = 700 N north F3 = 500 N west F4 = 600 N south What is the acceleration of the object?

A person has a mass of 45 kg. How much does she weigh on the Moon, where g = 1.62 m/ s2?

An astronaut weighs 99.0 N on the Moon, where the acceleration of gravity is 1.62 m/ s2. How much does she weigh on Earth?

FIGURE 4-11 -The free-body diagram of an 8.00 kg object is shown in Fig. 4-11. What is Newton's Second Law for this object?

A 1.0-kg object is moving with a constant velocity 2.0 m/s toward the north. There are two forces acting on the object. One of the forces is 2.0 N north. The other force is ________

A 1200-kg car starts from rest and accelerates with constant acceleration, traveling 200 m in 9.00 s. What is the force of the road on the car during this acceleration?

A 5.00-kg object is initially at rest. The object is acted on by a 9.00-N force toward the east for 3.00 s. No force acts on the object for the next 4.00 s. How far has the object moved during this 7.00 s interval?

FIGURE 4-9 -The two forces indicated in Fig. 4-9 act on a 3.00-kg object. What is the acceleration of the object?

A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/ s2 toward the east?

A force of 120 N is applied to an object whose mass is 30 kg. The object's acceleration is

Two objects push on each other. The first object has a mass 30.0 kg and it accelerates at 2.00 m/s² toward the east. The second object has a mass 7.00 kg. If no other forces are acting on the objects, what is the acceleration of the second object?

Two forces act on a 4.00-kg object in a manner that the object has an acceleration 3.00 m/s² in a direction 20.0° north of east. The first force is 15.00 N in a direction 10.0° west of north. What is the second force?

The following four forces act on a 4.00 kg object: F₁ = 300 N east F₂ = 700 N north F₃ = 500 N west F₄ = 600 N south What is the acceleration of the object?

A person has a mass of 45 kg. How much does she weigh on the Moon, where g = 1.62 m/ s²?

An astronaut weighs 99.0 N on the Moon, where the acceleration of gravity is 1.62 m/ s². How much does she weigh on Earth?

A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/ s² toward the east?