College Physics Exam 2

The normal force is

The force of a surface on an object that is perpendicular to the surface

Which of these is a part of the definition of a force?

Acts on an object, A push or a pull, Requires an agent to create the force.

The symbol used for a frictional force is

f

The frictional force is

Parallel to the surface the object is on

Newton’s first law says

An object’s velocity will be constant (both speed and direction) as long as no force acts on it.

The tendency of an object to resist a change in its motion is known as

Inertia

The acceleration of an object has what kind of relation to the mass of the object?

Inverse

The gravitational force of the Earth on an object close to the surface is also known as

Weight

Dynamics, or the study of forces, is the study of

The causes of motion

The acceleration of an object has what kind of relation to the force applied?

Linear

If the net force on an object is zero, what can be said about the vectors on a free body diagram

The vector sum is zero

Newton’s 3^rd law says

All forces occur as a part of an action/reaction pair

When a cat jumps from the floor onto a table, what can be said about the force on the floor

The force of the floor on the cat is equal to the force of the cat on the floor

The net force on an object is

In the same direction as the acceleration

The other force in the action/reaction pair of a hammer striking a nail in a wall is

The force of the nail on the hammer

A free body diagram should include

A coordinate system, The object represented as a dot, All forces represented as vectors.

How are acceleration and force related?

Acceleration is directly proportional to force

Units of force

Newtons (N), or lb (pounds)

The net force on an object is

The vector sum of all the forces on the object

An example of a long-range force is

Weight

How are the mass (m) and weight (w) of an object related?

w = mg

If an object is in equilibrium, what does Newton’s 2^nd law tell us?

The net force is zero.

Is the net force larger when an object is in static equilibrium or dynamic equilibrium?

Net force for both is zero.

What can be said about the net force on an object when its velocity is changing?

Net force is in the same direction as the acceleration.

An object near the Earth seems ‘weightless’ if

It is in free fall

The y component of an object’s acceleration is determined by

The y components of all the forces on the object

The acceleration in the x-direction is determined by the

Sum of the x-components of all forces acting on the object

How can the apparent weight of on object be measured?

A simple scale

An object in dynamic equilibrium is

Moving with a constant velocity

Riding in an elevator, when is your weight different than your apparent weight?

Any time an elevator’s speed is changing

How does the coefficient of static friction usually compare to the coefficient of kinetic friction?

Static > kinetic

The normal force on an object is always

Perpendicular to the surface the object is in contact with

Is the normal force affected by any other forces?

Yes, it is changed by forces that are parallel to the normal force.

In order for a bicycle wheel to roll on the street the bottom of the wheel must

Be stationary

When trying to slide an object on a rough surface, what requires a larger force?

Getting it started

Which of these does the kinetic frictional force not depend on?

Speed of the motion

When two objects are connected by a string how are the tension forces on each object related?

The tension forces on each object are the same

The kinetic frictional force is proportional to

The normal force on the object

If the velocity of a moving object is not changing, then

The net force is zero (dynamic equilibrium)

What approximations are made when dealing with pulleys and ropes in chapter 5?

The pulley is frictionless, and the pulley and string are both massless

How does a massless, frictionless pulley change the tension in a string?

Changes the direction of the tension

When an object’s velocity is decreasing

The net force and the acceleration are opposite the motion

When objects are in contact with each other and moving together how are the accelerations of each object related?

They have the same acceleration

When analyzing an interaction involving three interacting objects how many free body diagrams need to be drawn?

3 – one for each object

Which of Newton’s laws are important for analyzing interacting objects?

The 2^nd and 3^rd laws

The time for an object to complete one revolution is called the

Period

How does banking a curve on the highway allow cars to drive at a higher speed in the curve?

The normal force provides some centripetal acceleration.

A car driving around a corner at a constant speed has

Acceleration toward the center of the curve

At what point on a roller coaster loop is your apparent weight the greatest

Bottom

What is the force, F, needed to keep an object with mass m in a circular path with radius r at a constant speed v?

F = mv²/r (a=v²/r)

The maximum safe speed to turn a corner depends on

The static friction between the tires and the road

According to the book, your maximum walking speed is determined by

The length of your leg

The centrifugal force

Is not an actual force

How are period (T) and frequency (f) in circular motion related?

T = 1/f

The critical speed for traveling around a vertical loop

Is the speed at which the normal force is zero at the top, Depends on the radius of the loop, Is the slowest possible speed that can still complete the loop

The acceleration due to gravity near the surface of the moon depends on

The mass and radius of the moon

Two planets have the same mass, but planet X has twice the radius of planet Z. How does the acceleration due to gravity compare between the two?

Acceleration due to gravity is larger on Z

Which of these is in free fall around the Earth?

The moon, The international space station, GPS satellites

The speed of a satellite in a circular orbit around a star does not depend on

The mass of the satellite

Newton’s Law of Gravity says the gravitational force between two objects is related to the distance, r, between them as

1/r²

The period of a satellite orbiting a planet does not depend on

The mass of the satellite

An object in orbit around the Earth

Is in free fall

A satellite is in a circular orbit around the Earth. What mass(es) does the orbital speed depend on?

Mass of the Earth only

The feeling of weightless near the Earth means

The object is in free fall

As the distance between 2 objects increases, what happens to the force of gravity between them?

The force decreases.

Tangential acceleration is equal to (α is angular acceleration)

α*r

Every point on a rotating rigid body has the same

Angular velocity

An object moving in uniform circular motion has

Constant angular velocity

Torque depends on

Distance, r, of applied force from pivot point, Angle of the applied force, Magnitude of the force applied

Angular velocity is positive for

counterclockwise rotation

The center of gravity of an extended object

Can be calculated from the center of gravity of individual pieces of the object

If the center of gravity of an object is below its pivot point, the object will

Experience counterclockwise torque due to gravity

Which is true for a rotating object (α is angular acceleration)?

a_cp > 0 even when α=0

The unit for angular position used in this chapter is

Radians

Which situation creates the largest torque for the same amount of force

Long r with force perpendicular to radial line

How are angular acceleration, α, and torque, τ, related for a single particle with mass m revolving at a distance r from the rotation axis?

α = τ/(mr²)

Newton’s 2nd law for rotation says α is proportional to

τ_net

Rolling motion

Depends on a momentarily stationary pivot point, Is a combination of linear and rotational motion, Has a different speed for each point on the object

A car is moving at 10 m/s. What is the speed of the point on the tire which is in contact with the road?

0 m/s

The moment of inertia of an extended object depends on

Mass of the object, The shape of the object, Location of the rotation axis

An object is connected to a string which goes over a pulley which has mass and a radius R. How is the acceleration of the object, a, related to the rotation of the pulley?

a = αR

An object is connected to a string which goes over a pulley which has mass and a radius R. How is the speed of the object, v, related to the rotation of the pulley?

v = ωR

What has the larger moment of inertia, a cylindrical disk or a cylindrical hoop? They have the same mass and radius.

Hoop

How does including the mass and radius of a pulley change the time for a bucket attached to a string going around a pulley to fall?

Increases the time for the bucket to fall

What is the rotational analog to mass?

I