Question 1

The Moon is accelerated toward the earth,so it is gradually getting closer to the earth.

Accepted Answer

The Moon is actually moving away from the Earth at an average rate of about 3.8 centimeters per year, due to tidal interactions between the Earth and the Moon.

Question 2

When a car goes around a banked circular curve at the proper speed speed for the banking angle,what force cause it to follow the circular path?
A)the normal force from the road
B)the friction force from the road
C)gravity
D)No force causes the car to do this because the car is traveling at constant speed and therefore has no acceleration.

Accepted Answer

When a car goes around a banked circular curve at the proper speed, the normal force from the road provides the centripetal force necessary to keep the car moving in a circular path. This force is perpendicular to the road surface and is directed towards the center of the curve. It is balanced by the force due to gravity acting vertically downwards. The friction force from the road also plays a role in keeping the car from slipping, but it is not the primary force that causes the car to follow the circular path.

Question 3

An object moves in a circular path at a constant speed.Compare the direction of the object's velocity and acceleration vectors.
A)Both vectors point in the same direction.
B)The vectors point in opposite directions.
C)The vectors are perpendicular to each other.
D)The acceleration is zero but the velocity is constant.

Accepted Answer

When an object moves in a circular path at a constant speed, its velocity vector is tangent to the circle, pointing in the direction of motion. At any point along the path, the object's acceleration vector is directed toward the center of the circle, perpendicular to the velocity vector. Therefore, the velocity and acceleration vectors are perpendicular to each other.

Question 4

Three boxes are pulled along a horizontal frictionless floor by a constant horizontal pull P.The boxes are connected by very light horizontal strings having tensions T₁ and T₂ as shown in the figure.Which of the following statements about the tensions is correct? (There could be more than one correct choice. ) A)T₁ = P B)T₂ = P C)T₁ + T₂ = P D)T₂ > T₁ E)T₁ > T₂

Accepted Answer

The answer of Three boxes are pulled along a horizontal...

Question 5

In the figure,what does the spring scale read? The pulleys are ideal and the strings and scale are also massless. 
A)exactly 2.0 N.
B)exactly 1.0 N
C)0.50 N
D)0.00 N
E)more than 19.6 N

Accepted Answer

Since the pulleys and strings are massless and the system is in equilibrium, the tension in both strings must be equal. Therefore, the force exerted by string on spring scale is 1 N.

Question 6

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same. 
Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the lower block,B?
A)

B)

C)

D)

E)None of these diagrams is correct.

Accepted Answer

The correct free-body diagram of the horizontal forces acting on the lower block B would have a force arrow pointing to the left, representing the frictional force opposing the motion, and an arrow pointing to the right representing the tension force of 100 N applied to both blocks. Option B correctly shows these two forces acting on block B. Option A shows a force arrow pointing down (the weight of the block) and doesn't include the frictional force. Option C shows a normal force arrow pointing up, which is correct, but no force arrow representing the frictional force. Option D shows force arrows pointing in opposite directions, which is not possible when the blocks are moving together at a constant velocity. Option E is not a valid choice since one of the diagrams must be correct.

Question 7

A push of magnitude P acts on a box of weight W as shown in the figure.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The normal force on the box due to the floor is equal to 
A)W.
B)W + P.
C)W + P cos θ.
D)W + P sin θ.
E)W - P sin θ.

Accepted Answer

The answer of A push of magnitude P acts on...

Question 8

As shown in the figure,a woman is straining to lift a large crate,but without success because it is too heavy.We denote the forces on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person,C is the magnitude of the vertical contact force on the crate by the floor,and W is the weight of the crate.How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate? 
A)P + C = W
B)P + C < W
C)P + C > W
D)P = C

Accepted Answer

The answer of As shown in the figure,a woman is...

Question 9

Two cars go around a banked curve at the proper speed for the banking angle.One car has tires with excellent traction,while the other car has bald slippery tires.Which of these cars is more likely to slide on the pavement as it goes around the curve?
A)the car with the new tires
B)the car with the bald tires
C)Neither car will slide.
D)It depends on if the pavement is wet or dry.

Accepted Answer

When a car goes around a banked curve at the proper speed for the banking angle, the banking itself provides the necessary centripetal force to keep the car on the curve, regardless of the tire condition. Therefore, neither car will slide if they are at the correct speed for the banked curve.

Question 10

When an object moves in uniform circular motion,the direction of its acceleration is
A)in the same direction as its velocity vector.
B)in the opposite direction of its velocity vector.
C)is directed toward the center of its circular path.
D)is directed away from the center of its circular path.
E)depends on the speed of the object.

Accepted Answer

The acceleration of an object moving in uniform circular motion is always directed towards the center of the circular path. This acceleration is called centripetal acceleration, which keeps the object moving in a circular path.

Question 11

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same. 
Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the upper block,A?
A)

B)

C)

D)

E)

Accepted Answer

The answer of Two blocks,A and B,are being pulled to...

Question 12

Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord.The mass of P is greater than that of Q.A horizontal force 
Is applied to box Q as shown in the figure,accelerating the bodies to the right.The magnitude of the force exerted by the connecting cord on body P is 
A)zero.
B)less than F but not zero.
C)equal to F.
D)greater than F.

Accepted Answer

Since box P has a greater mass than box Q, it will require a greater force to accelerate it at the same rate. Therefore, the force exerted by the connecting cord on box P must be greater than the force exerted on box Q. However, it cannot be greater than the applied force of 11ea6c4e_0025_887c_9875_3dda9e16126b_TB6214_11 as the cord cannot exert a greater force than the force applied to it. Therefore, the force exerted by the connecting cord on box P must be less than the applied force but not zero, making choice B the correct answer.

Question 13

If you swing a bucket of water fast enough in a vertical circle,at the highest point the water does not spill out.This happens because an outward force balances the pull of gravity on the water.

Accepted Answer

At the highest point of the swing, the water does not spill out due to the centripetal force acting towards the center of the circle, which is provided by the tension in the bucket handle and not an outward force. Gravity acts downwards, and the centripetal force must overcome gravity to keep the water in the bucket.

Question 14

If a satellite moves with constant speed in a perfectly circular orbit around the earth,what is the direction of the acceleration of the satellite?
A)in the forward direction
B)in the backward direction
C)outward away from the earth
D)inward toward the earth
E)The acceleration is zero because the speed is constant.

Accepted Answer

The direction of the acceleration of the satellite is inward toward the earth due to the gravitational force. Even though the speed of the satellite is constant, its direction is changing constantly because its direction of motion is always tangent to the circular path. This change in direction causes the velocity vector to change, which is what causes the acceleration vector to point inward.

Question 15

In the figure,a 10-lb weight is suspended from two spring scales,each of which has negligible weight.Which one of the following statements about the readings in the scales is true? 
A)Each scale will read 5 lb.
B)The top scale will read zero,the lower scale will read 10 lb.
C)The lower scale will read zero,the top scale will read 10 lb.
D)Each scale will show a reading between one and 10 lb,such that the sum of the two is 10 lb.However,exact readings cannot be determined without more information.
E)None of these is true.

Accepted Answer

The answer of In the figure,a 10-lb weight is suspended...

Question 16

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice,causing the force of friction between the tires and the road to become zero.While the car is on the ice,it
A)moves along a straight-line path away from the center of the circle.
B)moves along a straight-line path toward the center of the circle.
C)moves along a straight-line path in its original direction.
D)continues to follow a circular path,but with a radius larger than the original radius.
E)moves along a path that is neither straight nor circular.

Accepted Answer

When the force of friction between the tires and the road becomes zero, the car can no longer follow the circular path because there is no centripetal force to keep it moving in a circle. According to Newton's first law of motion, an object in motion will stay in motion in a straight line unless acted upon by an external force. Therefore, the car will move along a straight-line path in its original direction at the point where it hit the ice.

Question 17

Two boxes,A and B,are connected by a horizontal string S on a horizontal floor.A very light wire pulls horizontally on box B,as shown in the figure,with a force of 100 N.The reaction force to this pull is 
A)the pull that box B exerts on string S.
B)the pull that string S exerts on box B.
C)the pull that string S exerts on box A.
D)the pull of box B on the wire.
E)the force that box A exerts on box B.

Accepted Answer

The answer of Two boxes,A and B,are connected by a...

Question 18

A car goes around a circular curve on a horizontal road at constant speed.What is the direction of the friction force on the car due to the road?
A)tangent to the curve in the forward direction
B)tangent to the curve opposite to the direction of the car's motion
C)perpendicular to the curve outward
D)perpendicular to the curve inward
E)There is no friction on the car because its speed is constant.

Accepted Answer

In this situation, the friction force will act inwards towards the center of the circle, perpendicular to the curve. This force is necessary to provide the centripetal acceleration required to keep the car moving in a circle at a constant speed.

Question 19

When a car goes around a circular curve on a horizontal road at constant speed,what force causes it to follow the circular path?
A)the normal force from the road
B)the friction force from the road
C)gravity
D)No force causes the car to do this because the car is traveling at constant speed and therefore has no acceleration.

Accepted Answer

The friction force from the road causes the car to follow the circular path. This force acts inwards towards the center of the circle, providing the centripetal force needed to maintain the circular motion. The normal force from the road also plays a role in balancing the weight of the car, but it does not directly cause the circular motion. The force of gravity is balanced by a normal force to keep the car on the road, but it does not cause the circular motion. Option D is incorrect because the car may be traveling at a constant speed, but it is changing direction, which means it has acceleration towards the center of the circle.

Question 20

A push of magnitude P acts on a box of weight W as shown in the figure.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The friction force on the box due to the floor is equal to 
A)P sin θ.
B)P cos θ.
C)0.
D)P cos θ + W.
E)P + W.

Accepted Answer

Since the box is at rest, the net force acting on it must be zero. The forces acting on the box are the push force P and the weight W, which are not in the same direction. The force of friction Ff acting on the box opposes the direction of motion, which is zero. Therefore, the force of friction Ff must be equal and opposite to the horizontal component of the push force, which is P cos θ. Thus, Ff = P cos θ.

Quiz 6: Applications of Newtons Laws

The Moon is accelerated toward the earth,so it is gradually getting closer to the earth.

When a car goes around a banked circular curve at the proper speed speed for the banking angle,what force cause it to follow the circular path?

An object moves in a circular path at a constant speed.Compare the direction of the object's velocity and acceleration vectors.

In the figure,what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

A push of magnitude P acts on a box of weight W as shown in the figure.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The normal force on the box due to the floor is equal to

Two cars go around a banked curve at the proper speed for the banking angle.One car has tires with excellent traction,while the other car has bald slippery tires.Which of these cars is more likely to slide on the pavement as it goes around the curve?

When an object moves in uniform circular motion,the direction of its acceleration is

If you swing a bucket of water fast enough in a vertical circle,at the highest point the water does not spill out.This happens because an outward force balances the pull of gravity on the water.

If a satellite moves with constant speed in a perfectly circular orbit around the earth,what is the direction of the acceleration of the satellite?

In the figure,a 10-lb weight is suspended from two spring scales,each of which has negligible weight.Which one of the following statements about the readings in the scales is true?

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice,causing the force of friction between the tires and the road to become zero.While the car is on the ice,it

Two boxes,A and B,are connected by a horizontal string S on a horizontal floor.A very light wire pulls horizontally on box B,as shown in the figure,with a force of 100 N.The reaction force to this pull is

A car goes around a circular curve on a horizontal road at constant speed.What is the direction of the friction force on the car due to the road?

When a car goes around a circular curve on a horizontal road at constant speed,what force causes it to follow the circular path?

A push of magnitude P acts on a box of weight W as shown in the figure.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The friction force on the box due to the floor is equal to