Newton's Second Law of Motion-Force and Acceleration

Accelerations are produced by __________.

a) masses

b) velocities

c) forces

d) accelerations

c) forces

The acceleration produced by a net force on an abject is _________.

a) inversely proportional to the mass of the object

b) in the same direction as the net force

c) directly proportional to the magnitude of the net force

d) all of the above

e) none of the above

d) all of the above

When an object reaches terminal velocity its acceleration is ________.

a) 9.8 m/s^2

b) 0 m/s^2

c) 4.9 m/s^2

b) 0 m/s^2

A heavy person and a light person parachute together and wear the same size parachutes. Assuming they open their parachutes at the same time, which person reaches the ground first?

a) the light person

b) the heavy person

c) neither - they both reach the ground together

b) the heavy person

A 10-kg brick and a 1-kg book are dropped in a vacuum. The net force of gravity on the 10-kg brick is _____.

a) zero

b) 10 times as much as the force on the 1-kg book

c) the same as the force on the 1-kg book

b) 10 times as much as the force on the 1-kg book

An apple weighs 1 N. When held at rest above your head, the net force on the apple is _________.

a) 1 N

b) 0 N

c) 9.8 N

d) 0.1 N

e) none of the above

b) 0 N

A girl pulls on a 10-kg wagon with a constant force of 30 N. What is the wagon's acceleration?

a) 0.3 m/s^2

b) 300 m/s^2

c) 10 m/s^2

d) 30 m/s^2

e) 3.0 m/s^2

e) 3.0 m/s^2

30 N/ 10-kg= 3

A push on a 1-kg brick accelerates the brick. Neglecting friction, to equally accelerate 10-kg brick, one would have to push _____.

a) with 100 times as much force

b) with one tenth the amount of force

c) with 10 times as much force

d) with just as much force

e) none of the above

c) with 10 times as much force

A block is dragged without acceleration in a straight-line path across a level surface by a force of 6 N. What is the frictional force between the block and the surface?

a) 6 N

b) more than 6 N

c) less than 6 N

d) need more information to say

a) 6 N

Pressure is defined as ______.

a) time per area

b) force per time

c) velocity per time

d) force per area

e) distance per time

d) force per area

The unit of pressure is _______.

a) the newton

b) newtons per meter

c) the meter

d) meters per second squared

e) newtons per square meter (or pascals)

e) newtons per square meter (or pascals)

The terminal speed for a person parachuting (with the chute open) is about _________.

a) 15 km/h

b) 150 km/h

c) 0 km/h

d) 1500 km/h

a) 15 km/h

If you pull horizontally on a crate with a force of 150 N and the crate doesn't move, the friction force must be 150 N. Now if you pull with 250 N so the crate slides at constant velocity, the friction force is ________.

a) more than 250 N

b) more than 150 N but less than 250 N

c) 250 N

c) 250 N

When the angle of an incline with a block resting on it increases, the normal support force _______.

a) decreases

b) increases

c) stays the same

a) decreases

A 10-N falling object encounters 10 N of air resistance. The magnitude of the net force on object is _________.

a) 4 N

b) 10 N

c) 0 N

d) none of the above

c) 0 N

A tow tuck exerts a force of 3000 N on a car, accelerating it at 2 m/s/s. What is the mass of the car?

a) 1000 kg

b) 3000 kg

c) 1500 kg

d) 500 kg

e) none of the above

c) 1500 kg

3000 kg/ 2 m/s/s= 1500

A 747 jumbo jet has a mass of 30000 kg. The thrust for each of four engines is 15000 N. What is the jet's acceleration when taking off?

a) 0.5 m/s^2

b) 2 m/s^2

c) 0.25 m/s^2

d) 1 m/s^2

e) none of the above

b) 2 m/s^2

a=f/m 1

step 1 4*15000 = force

= 60000 N

step 2 60000 N/30000 kg =2

A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the magnitude of the force acting on the car?

a) 500 N

b) 1000 N

c) 2000 N

d) 1500 N

e) none of the above

c) 2000

F= 1000*2

Suppose a cart is being moved by a force. If suddenly a load is dumped into the cart so that the cart's mass doubles, what happens to the cart's acceleration?

a) it quarters

b) it doubles

c) it stays the same

d) it quadruples

e) it halves

e) it halves

How much force is needed to accelerate a 2-kg physics book to an acceleration of 6 m/s^2?

a) 12 N

b) 0 N

c) 3 N

d) 0.33 N

e) 36 N

a) 12 N

F= ma 2 kg 6 m/s/^2= 12 N

The combination of all the forces that act on an object is called the net force.

True

The acceleration of an object is inversely proportional to the net force acting on it.

False

A steel ball and a wood ball of the came size are released together from the top of a tower. The absence of air resistance they both would reach the ground at the same time. The reason for this is that the force on the ball is the same.

False

Excluding the force due to air pressure, there is only one force acting on a book lying at rest on a tabletop.

False

The force that supports the weight of a book lying at rest on a tabletop is called normal force.

True

A fluid can be either a liquid or a gas.

True

The pascal is a unit of force.

False

It is possible for an object in free fall (no acceleration) to have zero acceleration.

False

Pressure is defined as the force one object exerts on another object.

False

The speed of an object dropped in air will continue to increase without limit.

False

You push with a 20 N on a 10-kg block and there are no opposing forces. How fast would the block accelerate?

a= f/m 20 N/ 10 kg=

2 m/s^2

You push with 20 N on a 10-kg block and there is a 10 N force of friction. How fast will the block accelerate?

20- 10 N/10 N

1.0 m/s^2

A 400,000-kg airplane in takeoff uses the 40,000 N thrust of each one of its four engines. What is the acceleration of the plane during the takeoff?

a=f/m

step 1 40,000 * 4= 160,000 N

step 2 160,000 N/ 400,000 kg=

0.4 m/s^2

An unbalanced force of 30 N gives an object an acceleration of 5.0 m/s^2. What force would be needed to give it an acceleration of 1.0 m/s^2?

m= f/g

step 1 30 N/ 5.0 m/s^2 = 6

step 2 6*1.0=

6.0 N

Suppose that you exert 400 N horizontally on a 50-kg crate on a factory floor, when friction between the crate and the floor is 200 N. What is the acceleration of the crate?

a=f/m

step 1 400 N- 200 N= 200 N

step 2 200 N/ 50-kg=

4 m/s^2

Bronco the skydiver, whose mass is 50-kg, experiences 200 N of air resistance. What is the acceleration of his fall?

step 1 bronco Fw 50-kg* 10= 500 N

step 2 50-kg - 200 N= 300 N

step 3 f/m 300 N/ 50-kg=

6 m/s^2

A 50-kg block of cement is pulled upward (not sideways!) with a foce of 800 N. What is the acceleration of the block?

300/50=

6.0 m/s^2