Physics Finals Test

A girl whose weight is 500-N hangs from the middle of a bar equallly supported by two vertical strands of rope. What is the tension in each strand?

250 N

Your friend climbed a vertical height of 5 meters. If their weight is 550 Newtons, how much work has your friend done?

2750 Joules

How far (distance) has an object gone if it moves at 8 m/s for 3.7 seconds? Round answer to the nearest tenth

28.6 m

A woman can lift barrels a vertical resistance distance of 4 meters (Dr) or can roll them up a 12 - meter long ramp (effort distance - De) to the same elevation. Calculate the mechanical advantage (MA)

3

A car initially moving at 10 m/s increases to 52 m/s after 7 seconds. What is the car's acceleration?

6 m/s2

A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car's acceleration?

6 m/s2

Mr. Hoffman climbed a vertical height (distance) of 10 meters. If his weight is 800 Newtons, how much work has he done?

8000 Joules

A pulley has two supporting strands and an M. A. of 2. In order for it to lift a load of 18 N (resisitance force - Fr), the person pulling will have to exert an effort force (Fe) of...

9 N

Ms. Kogl went to a Monster Truck rally. If Grave Digger, with a weight of 15,000 N, is able to jump a vertical height of 3 meters in 5 seconds, how much power is produced?

9000 Watts

Based on Conservation of Momentum, when two objects collide, the combined momentum is ____________ the total sum of each object's original momentum.

Equal to

Impulse

Equal to change in momentum; force times time

The amount of work done by walking up a staircase is...

Equal to the amount of work done running up the same staircase

Impulse

F*t

How much force is supplied if a horse uses 3300 J of work to pull a cart uphill 5.5 m?

F= 600N

When a person runs on an icy sidewalk and tries to stop quickly, she may keep moving forward. The reason this happens is because of...

Inertia

Momentum

Inertia in motion; mass times velocity

When you look at the speedometer in a moving car, you can see the cars...

Instantaneous Speed

What is terminal velocity?

The point at which a falling object's weight is balanced by air resistance (net force = 0) and the system is in equilibrium, which means that there is no acceleration

Acceleration

The rate at which velocity is changing; a vector quantity

A car's tires exert a force on the road. What provides the reaction force?

The road

An unfortunate bug splatters against the windshield of a moving car. Compared to the force of the car on the bug, the force of the bug on the car is...

The same

Instantaneous Speed

The speed at an instant; a scalar quantity

Which has more rotational inertia, a bicycle wheel or a solid disk of the same mass and diameter?

The wheel

The amount of potential energy possessed by an object on a shelf is equal to...

The work done in lifting it

In the absence of air resistance, at the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height, which ball hits the ground first?

They both hit the ground at the same time

Average Speed

Total distance covered divided by a total elapsed time; a scaler quantity

When you swing an object or dribble a ball around in a circle, in what direction is the force and acceleration pointed?

Toward the inside of the circle

A dropped dish is more likely to survive a fall on a carpet rather than concrete, because the softness of the carpet leads to the increased contact time

True

The total momentum of a firecracker or a bow and arrow is zero before and after firing because the momentum of the parts will cancel each other out given that they are moving opposing directions

True

Torque is a measure of how much force acting on an object causes that object to rotate

True

When boxers get punched, they should move their head away form the punch to increase the contact time and reduce the force

True

Double the mass of one car and you will get...

Twice (2 times) the momentum of the second car

When you jump off a step, you usually bend your knees as you reach the ground. By doing this, the time of the impact is 10 times more than what it would be in a stiff-legged landing. The average force on your body is...

1-10 the original force

If a freely falling object (no air resistance) had a speedometer, its speed would increase each second by approximately...

10 m/s

The acceleration due to gravity is symbolized by the letter g. What is the value of g on Earth's surface?

10 m/s2

What is the gravitational potential energy of a 50-kg mass lifted to a height of 20 meters? Remember that the acceleration due to gravity is approximately 10 m/s2

10,000 J

A 1.8-kg ball is thrown at 6.2 m/s. What is the ball's momentum?

11.2 kg*m/s

How much work does a boy do if he uses 15 N of force to move a wagon 125 m?

W= 1875 J

If the mass of an object is 20 kg and gravity on Earth is approx. 10 m/s2, what is the object's weight?

W= 200 N

Brett's backpack weighs 30 N. How much work is done on the backpack when he lifts it 1.5 m from the floor to his back?

W= 45 N*m = 45 Joules

The independent variable, which is often time, goes on the...

x- axis

When a car's speed(velocity) triples, its kinetic energy

Increases by nine times

When the lift is less than a helicopters weight...

The helicopter will move downward

When the lift is greater than a helicopters weight...

The helicopter will move upward

Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?

The large truck

What is terminal speed or velocity?

The maximum or end speed obtained while falling through our atmosphere

Terminal Velocity (2)

The maximum velocity an object will reach when falling through the air

Fw

m*ag

Potential energy (GPE)

m*g*h

Momentum

m*v

A 6-N falling object encounters 6-N of air resistance. What is the net force on the object?

0 N

A 60-kg object moves at 2 m/s. Its kinetic energy is...

120 J

A 20 N falling object encounters 4 N of air resistance. The net force on the object is...

16 N

If a pulley with a Mechanical Advantage of 4 moves an object a distance of 0.5 meters (dr), how far (de) will someone have to pull it down?

2 m

A jet on an aircraft carrier can be launched from 0 to 40 m/s in 2 seconds. What is the acceleration of the jet?

20 m/s

According to the Law of Conservation of Energy, if a car's engine puts out 45,000 Joules of energy and 15,000 Joules of that energy is used to move the car, how much energy is changed to other forms (heat, sound, etc.)?

30,000 J

Climbing the musical stairs at the Science Museum of Minnesota, if a person with a weight of 600 N goes up a vertical height of 6 meters in 12 seconds, how much power is produced?

300 Watts

What is the average speed of a cheetah that runs 99 meters in 3 seconds?

33 m/s

A 5-N force and a 30-N force act in the same direction on an object. What is the net force on the object?

35 N

Calculate the power of when you exerted 3600 Joules in a time of 10 seconds

360 Watts

Suppose that you exert 300-N horizontally on a 50-kg crate on a factory floor, where friction between the crate and the floor is 100-N. What is the acceleration of the crate?

4 m/s2

Calculate the power of Mr. Hansen when he exerted 3200 Joules in a time of 8 seconds

400 Watts

What is the Mechanical Advantage of a lever when you use 18 Newtons of force (Fe) to lift an object that weighs 90 Newtons (Fr)?

5

You use a 25 meter ramp (De) to raise a cart up a vertical height (Dr) of 5 meters. What is the Mechanical Advantage (MA) of the ramp?

5

A 4 kg ball has a momentum of 29 kg*m/s. What is the ball's velocity?

5 m/s

A 4-kg ball has a momentum of 20 kg·m/s. What is the ball's speed(velocity)?

5.0 m/s

How much force is needed to accelerate a 3.5-kg physics book to an acceleration of 1.5 m/s2?

5.3 N

An object on the Earth has a weight of 500 Newtons. What is the mass of the object? Use g = 10 m/s2

50 kg

A friend has a mass of 57 kg. On Earth, what is her weight? The acceleration due to gravity on Earth is approximately 10 m/s

570 N

Suppose you take a trip that covers 180 km and tales 3 hours to make. What is your average speed?

60 km/h

If 9000 J of work can be done in 15 seconds, how much power is produced?

600 Watts

An arrow in a bow has 70-J of potential energy. Assuming no transfer of energy to heat or sound, how much kinetic energy will it have after it has been shot?

70 J

Suppose you take a trip that covers 180 km in 2.5 hours to make. Your average speed is...

72.0 km/h

How many joules of work are done on box when a force of 25-N pushes it 3 m?

75 J

How much power is required to do 40-J of work on an object in 5 seconds?

8 W

How much force is needed to accelerate 4 kg physics book to an acceleration of 2 m/s2?

8.0 N

Using a lever, you push down with a force of 8 Newtons (Fe) in order to lift a rock. If the Mechanical Advantage (MA) of the system is 12, what is the weight (Fr) of the rock?

96 Newtons

Which of the following statements about a moving object is true?

A change in speed must change velocity

Relative Motion (Frame of Reference)

A description of an objects motion with respect to another object

Unbalanced Forces

A net force acts on the system; forces are unequal

Force Diagram

A picture used to show the relative magnitude and direction of forces acting on an object

Universal Law of Gravitation

A relationship between two objects where the attractive force is directly proportional to the product of the masses and inversely proportional to the square of the distance between them

Which object will have the greatest rotational inertia rolling down a ramp? A ring, solid disk, or neither?

A ring

Torque

A turning force

If a textbook which has a mass of 2.2 kg on Earth weighs 19.6 Newtons on Venus, what is the value of the gravitational acceleration there? Round to the nearest tenth.

Ag= 8.9 m/s2

On Earth, the horizontal component of an object's motion is affected by which of the following?

Air Resistance (Friction)

Centripetal Acceleration

An acceleration that is directed toward the center of a circle

System

An object or group of objects upon which a net force may act. Action and reaction forces cancel within a system

Projectile

Any object that moves through the air or space, acted on by only gravity (and air resistance, if any)

In which position will an ice skater spin the fastest?

Arms held in by the body

The resistance an object has to changes in its rotational state of motion is called rotational...

Inertia

An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the...

Arrow's push against the bowstring

Since Earth is attracted to the sun, why doesn't it fall into the sun?

Because it has sufficient tangential velocity

A vector is a quantity that has...

Both direction and magnitude

An object thrown into the air with a spin rotates about its...

Center of gravitu

If the sum of all the forces action on moving objects is zero, the object will...

Continue moving with constant velocity

You are on a frozen pond, and the ice starts to crack. If you lie down on the ice and begin to crawl, this will...

Decrease the pressure on the ice

A ball is tossed vertically upward. During this time the acceleration of the ball due to gravity is always...

Directed downward

To calculate the slope of a graph...

Divide the rise by the run (y2-y1)/(x2-x1)

Action/ Reaction Pairs

During any interaction, there is a balanced (equal and opposite) pair of forces acting

Law of conservation of energy

Energy cannot be created or destroyed. The total energy in a system remains the same even when energy changes form

Gravitational Potential Energy (GPE)

Energy given to a lifted object; mass times acceleration due to gravity times height

Kinetic Energy

Energy of a moving object; 1/2 times mass times velocity squared

Free Fall (2)

Falling under the influence of gravity but in the absence of air resistance

If you whirl (or spin) a tin can on the end of a string and the string suddenly breaks, the can will...

Fly off, tangent to its circular path

Newton's 3rd Law

For every action there is an equal and opposite reaction

Pressure

Force divided by area

Work

Force multiplied by distance (F*d)

Newton's 2nd Law

Force= mass times acceleration

Balanced Forces

Forces are equal and opposite; equilibrium

Mechanical Advantage using forces (MA)

Fr / Fe

Air Resistance or "Drag"

Friction caused by air particles; a vector quantity

Air Resistance

Friction caused by an objects motion through air

Halve the mass of one car and you will...

Have half (1/2) the momentum of the second car

What happens when an ice skater pulls in his hands while turning?

He will turn (spin) faster

Forces always occur...

In pairs

Law of Conservation of Momentum

In the absence of a net external force, the momentum of an object or system of objects is unchanged

The reason passed dashboards and bumpers are used in cars that they...

Increase the time of impact in a collision

A block is at rest on an incline. The force of friction necessary to prevent the block from sliding increases when the incline angle is...

Increased

A ramp 8 m long is next to a table that is 1.5 m high. Which will require less force, lifting a heavy box straight up to the table or pushing it up the ramp?

Less force is required to push the block up the ramp, although it goes a longer distance

If an object has a weight of 494 Newtons, what is its mass on Earth? Round to the nearest tenth. Hint: You need to use the acceleration due to gravity on Earth to solve this problem!

M= 49.4 kg

Weight

Mass times gravity (m*g)

The momentum of an object is defined as the object's...

Mass times it's velocity

On a merry-go-round, which horse has the greatest rotational speed/velocity?

Neither

A mother is holding her child with a weight of 65 Newtons at a distance of 1.2 meters off the floor. How much work is she doing?

No work is done

Mr. Nygren is holding a basketball with a weight of 9 Newtons at a distance of 1.5 meters off the floor. How much work is he doing?

No work is done

Which objects roll down an incline with the greatest acceleration?

Objects with small rotational inertia

Kinetic energy of an object is equal to...

One half the product of its mass times its speed(or velocity) squared

On a merry-go-round, which horse is travelling with the greatest tangential speed/velocity?

Outside

How much power is required to lift a 50 N box up 3 meters in 1.2 seconds?

P= 125 W

You do 65 Joules of work on an object in 4.3 seconds. How much power do you use?

P= 15.1 W

A person is able to lift 750 N of force up a 2.5 meter stairwell in 12 seconds. How much power is used?

P= 156.3 Watts

A teenager performs 250 J of work in 5 seconds. How much power is used?

P= 50 Watts

Double the mass and double the velocity of one car and you will...

Quadruple (4 times) the momentum of the second car

Vector Quantities

Quantities such as force and displacement which have both magnitude and direction

Scalar Quantities

Quantities such as mass and distance which have only magnitude

Rotational Speed/ Velocity

Rate of rotation; also called angular speed

Rotational Inertia

Resistance of an object to changes in its rotational motion

Slope

Rise/ run or the change in the y- variable with respect to a change in the x- variable

Velocity

Speed in a given direction; a vector quantity

Tangential Speed/ Velocity

Speed/ velocity of an object moving along a circular path; calculated the same as linear speed

The action is your foot applies a force to a ball. The reaction force is...

The ball applies a force to your foot

Terminal Velocity

The end or highest speed possible to attain for a falling object; air resistance balances/ is equal to the pull of gravity on an object

Free Fall

The fall of an object with only the force of gravity acting on it

When a lift is equal to a helicopters weight...

The helicopter will hover in midair

The main difference between objects in static and dynamic equilibrium is...

While both situations involve a net force of zero, in static equilibrium the object is at rest and in dynamic equilibrium the object is moving at a constant rate.

Power

Work divided by time (W/t)

Power

Work divided by time; rate at which work is done (W/t)

An object is moved slowly, and an identical object is moved quickly. If the distance that they move is the same, is the amount of work done the same? Hint: Think Stair Lab!

Yes

A pulley system (or other simple machines like a lever) can...

change the direction of the effort force (you pull down, object moves up) and multiply the force (decrease the total effort force as compared to the resistance force)

Mechanical Advantage using distances (MA)

de / dr

Kinetic energy (KE)

½ * m * vs