Physics Dynamics Test

In the figure to the right, two boxes of masses m and 4m are in contact with each other on a frictionless surface. What is the force causing the acceleration of the more massive box?

4F/5

An elevator of mass M is pulled upwards by a cable; the elevator has a positive, increasing, velocity. What is the tension in the cable (neglecting the mass of the cable)?

Greater than Mg

In the Atwood machine, shown on the diagram, two masses M and m are suspended from the pulley, what is the magnitude of the acceleration of the system? (Ignore friction and the mass of the pulley. M>m)

(M-m)g/M+m

Which of the following is an example of a force which acts at a distance (without contact)?

Gravity

An elevator of mass M is pulled upwards at constant velocity by a cable. What is the tension in the cable (neglecting the mass of the cable)?

Equal to Mg

A block with initial velocity of 3m/s slides 9m across a rough horizontal surface before coming to rest. What is the coefficient of kinetic friction?

0.05

In the diagram shown above, two blocks A and B with masses m and 2m are in contact on a horizontal frictionless surface. A force F is applied to block A. What is the force exerted by block A on block B?

2F/3

A system of two blocks (3kg and 5kg) is accelerated by an applied force of magnitude F on the frictionless horizontal surface. The tension in the string between the blocks is:

3/8 F

An elevator of mass M is pulled upwards by a cable; the elevator has a positive, but decreasing, velocity. What is the tension in the cable (neglecting the mass of the cable)?

Between zero and Mg (because it is still going upwards, so it has to be greater than zero)

A locomotive is pulling an empty freight car with a constant acceleration on a horizontal surface. The mass of the locomotive is five times the mass of the car. Which statement is true about the force applied by the car on the locomotive?

Equal to the force of the locomotive on the car

In the figure to the right, two boxes of masses m and 3m are connected by a string while a force F is pulling on the more massive box; what is the acceleration of the less massive box?

F/(4m)

In the figure to the right, two boxes of masses m and 4m are in contact with each other on a frictionless surface. What is the acceleration of the more massive box?

F/(5m)

In the diagram shown above, two blocks A and B with masses m and 2m are in contact on a horizontal frictionless surface. A force F is applied to block A. What is the acceleration of the system two blocks?

F/3m

In the figure to the right, two boxes of masses m and 3m are connected by a string while a force F is pulling on the more massive box; what is the tension force in the string between the boxes?

F/4

Two blocks are attached by a compressed spring and are initially held at rest on a frictionless surface. The blocks are then released simultaneously. If block I has four times the mass of block II, which of the following quantities is the same for both blocks as the spring pushes the two blocks away from each other?

Force on each block

A horizontal force is exerted on an object so that it accelerates at a constant rate across a rough horizontal surface (friction cannot be neglected). The applied force is then doubled; what happens to the object's acceleration?

It increases to more than double its original value

Which Newton's law can explain the following statement that we often see on the highway display: "Buckle up-it's the State Law"?

Newton's First Law

When a baseball is struck by a bat, the force of the bat on the ball is equal and opposite to the force of the ball on the bar. This is an example of:

Newton's third law

A spacecraft travels at a constant velocity in empty space far away from any center of gravity. Which of the following about the force applied on the spacecraft is true?

No applied force is required to maintain a constant velocity

A passenger standing in a moving bus, facing forward suddenly falls forward. This can be an indication of what?

The bus slows down

A passenger standing in a moving bus, facing forward suddenly falls backward. This can be an indication of what?

The bus speeds up

A passenger standing in a moving bus, facing forward suddenly falls to the right. This can be an indication of what?

The bus turns to the left

A car traveling at 40 m/s strikes a mosquito. Which of the following is the true statement?

The force on the mosquito is equal to the force on the car

A loaded truck collides with a car causing huge damage to the car. Which of the following is true about the collision?

The force on the truck is the same in magnitude as the force on the car

A boy rides a bicycle at a constant velocity. Which of the following about the net force is true?

The net force is zero

Earth pulls downward on a pen, of mass m, which is sitting on a table; the magnitude of the force is mg. If that is called the action force, what is the reaction force?

The pen pulling upward on earth with a force equal to mg

A railroad wagon pushes down on a railroad with a force of 200 kN. Which of the following is the "reaction force"?

The railroad pushes up the wagon with 200 kN

A traffic light is suspended from a cable. Earth pulls downward on the traffic light with a force of 1500 N. If this is the "action force", what is the "reaction force"?

The traffic light pulling upward on Earth with a 1500 N force

The Earth pulls down on a railroad wagon with a force of 200 kN. Which of the following is the "reaction force"?

The wagon pulls up the Earth with 200 kN

A hammer and a pebble are dropped simultaneously from the same height. Neglect air resistance.

They both accelerate at the same rate because they have the same weight to mass ratio

A box is being pushed by a constant force along a horizontal surface. If the object's velocity is constant, we can infer that there is _________ acting on the box:

a frictional force

A net force acts on a mass m and produces an acceleration a. What acceleration results if a net force 3F acts on mass 6m?

a/2

A net force F accelerates a mass m with an acceleration a. If the same net force is applied to mass 5m, then the acceleration will be:

a/5

If you exert a force F on an object which has a much greater mass than you do, the force which the object exerts on you will:

be of magnitude F and in the opposite direction

Mass and weight:

both have different measuring units

Action-reaction forces are:

equal in magnitude and point in opposite directions

A ball is thrown straight up. At the top of its path, the magnitude of the net force acting on it is:

equal to mg

A soccer player kicks a soccer ball with a force of 1300 N. The soccer ball hits the player with a force of:

exactly 1300 N

A block of mass 4m can move without friction on a horizontal table. This block is attached to another block of mass m by a string that passes over a frictionless pulley. If the masses of the string and the pulley are negligible, what is the magnitude of the acceleration of the descending block?

g/5

If a book on the dashboard of your car suddenly flies towards you, the forward velocity of the car must have:

increased

The acceleration of an object is inversely proportional to:

its mass

In the absence of a net force, a moving object will:

move with constant velocity

When the engines on a rocket ship in deep space, far from any other objects, are turned off, it will:

move with constant velocity

Newton's third law refers to "action-reaction forces". These forces always occur in pairs and:

never act on the same object

The acceleration due to gravity is higher on Jupiter than on Earth. The mass and weight of a rock on Jupiter compared to that on Earth would be:

same, more

The acceleration of an object is proportional to:

the net force acting on it

In order for a rocket ship in deep space, far from any other objects, to move in a straight line with constant speed it must exert a net force that is:

zero

When a cat sleeps on a table, the net force on it is:

zero