SCI 190 - Review Questions for Chapter 2, 4 and 5

State Newton's First Law in your own words?

An object in uniform motion or at rest will stay in uniform motion or at rest unless acted upon by an outside force

State Newton's Second Law in your own words?

Acceleration of an object is directly proportional to the net force acting upon it and inversely proportional to its mass. Fnet=ma

State Newton's Third Law in your own words?

For every action, there is an equal and opposite reaction. Forces always occur in pairs that have an equal magnitude but opposite directions

Write down Newton's Second Law in mathematical form?

Fnet=ma

What is meant by the net force?

Sum of all forces acting on an object (magnitude and direction). Fnet=ma

What is meant by the resultant force?

Represents the combined effect of multiple forces taking into account magnitude and direction. Same thing as net force

How is the acceleration of an object related to the net force on that object?

Directly propotional. Higher acceleration=higher net force. Lower acceleration=lower net force

Does the net force determine completely the acceleration of an object?

Yes

If the net force on an object is constant, what can you say about the acceleration?

It will also be constant

If the net force on an object is constant, what can you say about the velocity?

It will change at a constant rate and have uniform motion

If the net force on an object is constant, what can you say about the speed?

Speed will change at a constant rate as long as all other factors also remain constant

If the net force on an object is zero, what does that imply about the acceleration of that object?

Acceleration will also be zero

If the net force on an object is zero, what does that imply about the velocity of that object?

Constant velocity or velocity in uniform motion. Example of Newtons First Law of Inertia

Cite some differences between mass and weight?

Weight: force against gravity. Mass: All the stuff you have. w=mg

What is the weight of 3 Kg mass?

w=30

What is the magnitude of the force that the earth exerts on a 3 Kg mass?

30

What is the magnitude of the acceleration of a freely falling 3 Kg mass?

10m/s

What is the magnitude of the acceleration of a freely falling 6 Kg mass?

10m/s

What is meant by inertia?

Resistance to changing your velocity (tendency to not want to move)

Which one has a large inertia? A 30 Kg mass or 60 Kg mass?

60kg

Is your weight smaller or larger on the moon compared to its value on the earth?

Smaller because of gravitational difference

If the earth attracts the moon, does that mean that the moon also attracts the earth?

Yes they are both pulling at each other (Newtons 3rd Law)

How do the magnitudes of two forces the moon and the earth exert on each other compare?

The magnitudes of the two forces are equal (Newtons 3rd Law)

What is the magnitude of the acceleration of a 2000 kg car when a net force of 4000 Newtons is applied to it?

a=2

If you apply the same net force to two objects with different masses, which one will have the larger acceleration?

Smaller one will have larger acceleration

What net force must you apply to a 1 kg object to give it an acceleration of 1 m/s2?

Fnet=1

What is the force required to keep an object moving at a constant velocity in the absence of all types of friction?

You don't need a certain type of force (trick question)

As you around a curve on a flat part of a road in a car at a speed of 45 m/s, what is the one force that prevents your car from skidding out of the road?

Friction

What is meant by terminal speed?

Objects weight=force of air resistance. No net force and no acceleration

How many forces are acting on a projectile in the absence of air resistance at the top of its path?

1 (force due to grvaity)

How many forces are acting on a projectile on the way up to its top position in the absence of air resistance?

One

How many forces are acting on a projectile on the way down from its top position in the absence of air resistance?

One

How many forces are acting on a freely falling object on the way up to its top position?

One

How many forces are acting on a freely falling object on the way down from its top position?

One

How many forces are acting on a freely falling object at top of its path?

One

Why is it dangerous to drive above posted speed limits when you round a curve?

Friction gives certain amount of wiggle room and speed can overcome the friction

Why is it dangerous to drive at high speeds when it is wet or icy?

Less friction for tires on the road

What is the source of the force that keeps you on the road when you are driving in a flat circular road?

Friction

What is the net force on an object that has reached terminal speed?

Zero

What is the force due to air resistance when a 500 Kg falling object reaches its terminal speed?

5000N

What is the net force on a freely falling 2 Kg object?

Fnet=20

What is the net force on a 3 Kg freely falling object at the top of its path?

Fnet=30

What is the magnitude of the acceleration of a 2 Kg object falling through air when air resistance on it is 4 N?

a=8

You throw a 2 Kg object straight up into the air. What is the magnitude of theacceleration of this object if it encounters 4 N of air resistance on the way up, after it has left your hand?

a=12

You throw a 2 Kg object straight down. What is the magnitude of the acceleration of this object if it encounters 4 N of air resistance on the way down, after it has left your hand?

a=8

A 4 Kg mass is moving on a circle with a constant speed of 8 m/s. What is the magnitude of the acceleration of this mass if the circle has a radius of 2 m?

a=32

A 4 Kg mass is moving on a circle with a constant speed of 8 m/s. What is the magnitude of the net force on this mass if the circle has a radius of 2 m?

Fnet=128N

A 2 Kg mass is falling straight down through air with decreasing acceleration. Is the speed of this object increasing or decreasing?

Increasing but at a slower rate

You throw an object straight up into the air. What happens to the magnitude of the force due to air resistance on the object as the object rises, after it has left your hand?

Force due to air resistance is proportional to speed. Magnitude of force will decrease on the way up.