physics sem. 2 final

A newton is equivalent to which of the following quantities?

(kg)(m/s^2)

The cable of a freight elevator applies a 3000-N force to accelerate a 250-kg elevator upward. Fill in all blanks. (Use the approximation that g ~ 10 m/s/s.) Enter positive numbers only. Ftens = Fgrav = m = Fnet = a =

- 3000 - 2500 - 250 - 500 - 2

For the following physical situation, identify the forces that are exerted upon the object. Select all that apply. A parachutist falls to the ground at a constant velocity.

- Air Resistance - Force due to gravity

What would have the effect of increasing the acceleration of an object?

- Decreasing the mass of the object - Doubling the net force experienced by the object - Halving the mass of the object

Which of the following would have the effect of increasing the acceleration of an object? - Decreasing the net force experienced by the object. - Tripling the mass of the object. - Doubling the net force experienced by the object. - Halving the mass of the object. - Decreasing the mass of the object.

- Doubling the net force experienced by the object. - Halving the mass of the object. - Decreasing the mass of the object.

For the following physical situation, identify the forces that are exerted upon the object. Select all that apply. A sign is suspended by two cables and hangs at rest.

- Force due to gravity - Tension

What COULD be true of an object that is at equilibrium?

- The object is moving with a constant velocity - The object is moving - The object is at rest

The motion of a rightward moving object is represented by the dot diagram below.

- The object is slowing down - The object is experiencing unbalanced forces

A skydiver pulls the chord of his parachute. The forces acting upon the skydiver and his parachute are shown in the diagram. From this diagram, one might infer that ____. Select all that apply.

- The skydiver will continue to fall, but now will slow down. - The skydiver will have an acceleration that is directed upwards.

For the following physical situation, identify the forces that are exerted upon the object.

- force due to gravity - normal force

When all individual forces acting upon an object are balanced, it is the natural tendency of the object to _____.

- keep their velocity constant (either at zero or non-zero) - maintain their state of motion

When all individual forces acting upon an object are balanced, it is the natural tendency of the object to _____. Select all that apply.

- keep their velocity constant (either at zero or non-zero) - maintain their state of motion

The motion of a leftward moving object is represented by a position-time graph. (Consider the positive direction to be to the right.)

- moving with Constant Speed - balanced forces

A sign is hung by two cables; each makes an angle of theta with the horizontal. As the angle theta is INCREASED, the weight of the sign ____, the tension force in the cable ____, and the vertical component of the tension force ____

- remains unchanged - decreases - remains unchanged

10-kg object is moving to the right at a constant velocity of 4 m/s. Which one of the following horizontal forces is required to maintain this state of motion

0 N

An object is accelerating at a rate of 4.2 m/s2 when the net force is decreased by a factor of 4.4 and its mass is increased by a factor of 3.9. The new acceleration will be _________ m/s2. Round to the nearest tenth (0.1).

0.2

A spring is stretched some amount. If the displacement of this spring was reduced by one-half, the elastic potential energy in the spring would change by a factor of

1/4

An object is accelerating at a rate of 10.8 m/s2 when the mass is increased by a factor of 4.9. The new acceleration will be _________ m/s2.

2.2

An object is accelerating at a rate of 10.5 m/s2 when the net force is decreased by a factor of 4.4. The new acceleration will be _________ m/s2. Round to the nearest tenth (0.1).

2.4

An object is accelerating at a rate of 10.2 m/s2 when the net force is decreased by a factor of 4.0. The new acceleration will be _________ m/s2.

2.6

An object is accelerating at a rate of 8.6 m/s2 when the mass is increased by a factor of 3.3. The new acceleration will be _________ m/s2. Round to the nearest tenth (0.1).

2.6

Ball A and ball B travel at the same speed; however, ball A has triple the mass of ball B. What is the ratio of the kinetic energy of ball A to ball B.

3:1

An object is accelerating at a rate of 9.9 m/s2 when the net force is increased by a factor of 3.4 and its mass is decreased by a factor of 1.5. The new acceleration will be _________ m/s2.

50.5

An object has a kinetic energy of 34 J. If the object's speed increases by a factor of 5, then its new kinetic energy will be ____ J.

850

In which of the following scenarios is work done?

A car decelerates while traveling on a flat stretch of road.

Two identical airplanes are flying over Omaha. airplane A is flying at twice the speed and twice the altitude (height above the ground) as airplane B. Compared to airplane B, what is the potential energy of airplane A?

A has twice the potential energy

In which of the following cases is no work done?

A weightlifter holds a barbell overhead.

Newton's First Law

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Force diagrams depicting the magnitudes and directions of the forces acting upon four objects are shown below. Each object has the same mass - approximately 5 kg.

CBDA

A dad gives his child on a sled a long push to set him in motion along the level surface. This situation can best be described as a transformation of

Chemical energy into Kinetic energy

The velocities and masses of four objects are shown. Rank these objects in order of their inertia, from least to greatest. (Type the four letters in the appropriate order with no spaces between letters.)

DACB

A sign with a mass of m is hung symmetrically from two cables which make an angle of theta with the horizontal (see diagram). The tension in each one of the cables is Ftens. The vertical component of the tension force is Fy; the horizontal component is Fx. Which of the following mathematical statements is true?

Fgrav = Fy + Fy

Newton's Second Law

Force equals mass times acceleration (F=ma)

An object of mass 'm' is resting upon an inclined plane with an incline angle of 'theta.' The coefficient of friction between the object and the plane is 'mu.' The object is at rest upon the incline. The free-body diagram is shown with the weight vector resolved into parallel and perpendicular components. Which of the following mathematical statements is correct?

Fparallel = Ffrict

What will increase the kinetic energy of an object?

Increasing the object's mass, increasing the object's speed

What are the units of the coefficient of friction?

It has no units

You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions?

It would have skidded four times farther

You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling three times as fast, what distance would the car have skidded, under the same conditions?

It would have skidded nine times farther

Jack and Jill are arguing in the cafeteria. Jack says that if he flings the jello with a greater speed it have a greater inertia. Jill argues that inertia does NOT depend upon speed, but rather upon mass. Who is correct?

Jill

SI unit for gravitational potential energy

Joule

SI unit for kinetic energy

Joule

SI unit for work

Joule

SI unit for elastic potential energy

Joules

SI unit for spring constant

N/m

Two cars collide head-on. At every moment during the collision, the magnitude of the force the first car exerts on the second is exactly equal to the magnitude of the force the second car exerts on the first. This is an example of

Newton's Third Law

A joule is equivalent to a

N•m

A hockey stick hits a puck on the ice. Identify an action-reaction pair in this situation.

The stick exerts a force on the puck; the puck exerts a force on the stick.

A truck weighs twice as much as a car, and is moving at twice the speed of the car. Which statement is true about the truck's kinetic energy compared to that of the car?

The truck has 8 times the kinetic energy of the car

A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a greater height?

They both slide to the same height

On Earth, more massive objects weigh more than less massive ones. (true or false)

True

SI unit for power

Watt

You throw a ball straight up. After it leaves your hand, compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

Work is - on the way up and + on the way down

Is it possible for a system to have negative potential energy?

Yes, since the choice of the zero of potential energy is arbitrary

A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that

a frictional force is acting on it.

Gravitational potential energy is always measured in relation to

a zero or reference level.

An object that is at equilibrium is an object upon which all the forces are ____.

balanced

Suppose that an astronaut throws a rock in outer space at a location far from significant influences of gravity and air resistance. One would expect that the rock would ____.

continue in motion with the same speed and direction

A box is being accelerated across a level surface. A force is being applied to the box in an upward and a rightward direction (as shown below). This force makes an angle of 30 degrees with the horizontal. If the angle at which the force is exerted is increased to 45 degrees, then the normal force would ____.

decrease

A box is being accelerated across a rough, level surface. A force is being applied to the box in an upward and a rightward direction (as shown below). This force makes an angle of 30 degrees with the horizontal. If the angle at which the force is exerted is increased to 45 degrees, then the friction force would ____.

decrease

Suppose that an object slows down while moving horizontally. In this situation, the object's kinetic energy would ____, its potential energy would ____ , and its total mechanical energy would ____

decrease, remains the same, decrease

An object is placed upon an inclined plane with an incline angle of 25 degrees. As the incline angle is INCREASED towards 90 degrees, the normal force experienced by the object ____.

decreases

If the net work done on an object is negative, then the object's kinetic energy

decreases

Consider the diagram of a force vector shown below. The angle theta is expressed as the angle of the vector with respect to due north. As the angle theta DECREASES from the current value to 0 degrees, the horizontal component of force ____ and the vertical component of force ____

decreases, increases

A rightward moving object is coasting to a stop along a straight, level surface. The net force acting upon the object MUST be ____.

directed leftward

Action-reaction forces are

equal in magnitude but point in opposite directions.

A rightward-moving object would naturally and ultimately come to rest in the absence of forces. A rightward force is required to keep such an object moving rightward. Inertia is the general name given to that force. (true or false)

false

Which of the following is the cause of an acceleration?

force

In order to have work done upon an object, there must be a(n) ____ to cause a(n) ____.

force acting upon the object, displacement

A free-body diagram represents all of the following except

forces exerted by the object.

A box is being accelerated across a level surface. A force is being applied to the box in a downward and rightward direction (as shown below). In this situation, the normal force is ____ the force of gravity.

greater than

Suppose that an object moves upward with an increasing speed. In this situation, the object's kinetic energy would ____, its potential energy would ____, and its total mechanical energy would ____

increase, increase, increase

An object is placed upon an inclined plane with an incline angle of 25 degrees. As the incline angle is increased towards 90 degrees, the parallel component of the weight vector ____.

increases

Consider the diagram of a force vector shown below. The angle theta is expressed as the angle of the vector with respect to due south. As the angle theta INCREASES from the current value to 90 degrees, the horizontal component of force ____ and the vertical component of force ____

increases, decreases

Mass is expressed in units of ____ and weight is expressed in units of ____

kilograms (kg) Newtons (N)

The main difference between kinetic energy and potential energy is that

kinetic energy involves motion, and potential energy involves position.

The length of a force vector represents the

magnitude of the force

The amount of matter or "stuff" in an object is referred to as the _____ of the object.

mass

Kinetic energy is the energy that an object possesses due to its ____ and potential energy is the energy that an object possesses due to its ____

motion, position

In order for an object to conserve its total mechanical energy it is absolutely necessary that

non-conservative (i.e., external) forces do NOT do net work upon the object

If you push twice as hard against a stationary brick wall, the amount of work you do

remains constant at zero.

Work is a ____ quantity; it is fully described by stating its ____.

scalar, magnitude alone

Some forces are categorized as conservative forces (or internal forces) while others are categorized as non-conservative forces (or external forces). Which of the following forces are generally categorized as conservative (or internal) forces?

spring force, force of gravity

The force that keeps you from sliding on an icy sidewalk is

static friction.

A block slides down a frictionless plane inclined at some angle above the horizontal. The gravitational force is directed

straight down toward the center of the Earth.

A quiet moment during a test is interrupted as a physics book falls from a table and strikes the floor. The reaction force to the force of the Earth pulling the book downwards is ____.

the book exerts an upward pull on the Earth

If the sign of work is negative

the displacement is in the direction opposite the force.

A vector component describes _____.

the effect of a vector in a given direction

Power is defined as

the rate at which work is done upon an object

A more powerful motor can do

the same work in a shorter time interval

Student A and student B are doing two identical tasks involving physical work. Student A does the task in more time than student B. In this physical situation

the two students do the same amount of work but student B has the greater power rating

The law of inertia (Newton's first law) applies _____.

to both moving and nonmoving objects

Which of the following is a true statement about the conservation of energy?

total energy is always conserved

Which of the following refers to the sum of kinetic energy and all forms of potential energy?

total mechanical energy

The acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object. (true or false)

true

The mass of an object on the moon will be the same as its mass on Earth. (true or false)

true

A free-falling object is an object ____.

upon which gravity is the only force

The force of gravity that acts upon an object is referred to as the _____ of the object.

weight

If both conservative (i.e., internal) and non-conservative (i.e., external) forces are doing net work upon an object, then the total mechanical energy of the object ____.

will definitely change

A dart is traveling through the air towards a dart board. Assume that air resistance is negligible. In this situation, the total mechanical energy of the dart

will remain constant

A roller coaster car is coasting down the first drop of the track. Assume that resistance forces have no effect on the car's motion. In this situation, the total mechanical energy of the car

will remain constant

A car decelerates while traveling on a flat stretch of road. Is work being done?

yes

If you were in a spaceship and fired a cannonball into frictionless space, the amount of force needed to keep the cannonball in motion would be ____.

zero, since no force is necessary to keep an object moving

It's more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because You Answered

µk < µs