Physical Science Exam 2

Granny whizzes around the ring and is suddenly confront with Ambrose at rest directly in her path. Rather than knock him over, she picks him up and continues in motion with 'braking.' Grannys Mass=50kg Granny Intial Speed 3 m/s Ambrose's mass-25kg Ambrose's initial speed 0 m/s What is the momentum of the Granny-Ambrose system before and after

150 kg m/s

Jacko, who has a mass of 60kg and stands at rest on ice, catches a 20 kg ball that is thrown to him at 10 km/h. How fast does Jacko and the ball move across the ice?

2.5 km/h 20kg x 10 kg/h= 200 kg(km/h) This is also the momentum after the catch where the moving mass is 80 kg. That's 60 kg for Jacko and 20 kg for the caught ball.

What 2 things enter where work is done?

Application of force, and movement of something by that force

A cannon recoils from firing a cannon ball. The speed of the cannons recoil is small because the

Cannon has more mass than the ball

Define inelastic collsion

Collision whereupon colliding objects become tangled or coupled together, generating heat

What are the principles of machines?

Conservation of energy: work input = work output Input force x input distance= output force x output distance (force x distance)input= (force x distance) output

What is potential energy?

Defined as stored energy due to position, shape, or state. In its stored state, energy has the potential for doing work. (drawn bow, stretched rubber band)

A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is

Doubled

Consider a problem that asks for the distance a fast-moving crate slides across a factory floor in coming to a stop. The most useful equation for solving this problem is

Fd=(change in)1/2 mv^2 The work-energy theorem is the physicist's favorite starting point for solving many motion-related problems.

What is the equation for impulse?

Force x time= ft=impulse

What does power measure?

How fast work is done

The change in momentum of an object is equal to the ?

Impulse applied to it Force x time= Change in momentum

What is impulse?

Impulse is the product of force and contact time

What does the law of conservation of momentum state?

In the absense of an external force, the momentum of a system remains unchanged. Total momentum before=total momentum after

The effects of energy are observed only when

Its being transferred from one place to another or its being transformed from one form to another

What are the units for work?

Joule.

What is the formula for kinetic energy?

KE=1/2 mass x speed^2 or 1/2mv^2

You drop a stone from a high cliff, as it falls compare its kinetic and potential energy

Kinetic increases, potential decreases

Small changes in speed mean what for changes in Kinetic energy

Large changes

If you push against a stationary brick wall for several minutes where are you doing work?

On your muscles, but not on the wall.

What is the equation for gravitational potential energy

PE= weight x height or PE=mgh

What is the equation for power

Power = Work done/ time interval

A job can be done slowly or quickly. Both may require the same amount of work, but different amounts of

Power. Power is the rate at which work is done

Is kinetic energy a vector or scalar quantity?

Scalar

Define energy

That which produces changes in matter

What is kinetic energy?

The energy of a moving body

What is work

The product of force exerted on an object and the distance the object moves (IN the same direction as the force.) Work is done only when the fore succeeds in moving the body it acts upon

A moving car has momentum. If it moves twice as fast, its momentum is...

Twice as much

Work is done in lifting a barbell. How much work is done in lifting a twice as heavy barbell the same distance

Twice as much

You do work when pushing a cart. If you push the cart twice as far with the same constant force, then the work you do is

Twice as much

The work done in braking a moving car to a stop is the force of tire friction stopping distance. If the initial speed of the car is doubled, the stopping distance is

Twice the speed means 4 times the kinetic energy and four times the stopping distance

Is momentum a vector, or scalar quantity?

Vector

What 2 categories does work fall into?

Work done against another force and Work done to change the speed of an object

What is the equation for work?

Work=force x distance

Does a car hoisted for repairs in a service station have increased potential energy relative to the floor?

Yes

Must a car with momentum have kinetic energy?

Yes, due to motion alone.

The kinetic energy of a pendulum is smallest

at the top of the swing

Your friend says that impulse equals momentum. This statement isn't correct, and the missing word is

change

whereas impulse involves the time that a force acts, work involves

distance that a force acts

If you lift a 10N weight vertically 10M above the floor you are

doing work against gravity

When a force that produces an impulse last twice as long the impulse it

doubled

When a force that produces an impulse last twice as long, the impulse is

doubled

A kilowatt hour is a unit that measures

energy

If a man firmly holds a gun when fired, then the momentum of the bullet is equal to the recoil momentum of the....

gun-man system

A cannon ball shot from a cannon with a long barrel will have a greater muzzle velocity because the cannon ball receives greater

impulse

What does the law of conservation of energy state?

in the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed

When the speed of an object doubles its momentum

increases by 2 times

what is momentum?

is inertia in motion defined as the product of mass and velocity: momentum = mv

An object that has potential energy may have this energy because of its

location

When direction is unimportant what is the equation(s) for momentum

momentum = mass x speed momentum = mv

An object that has kinetic energy must be

moving

Inelastic collisions are...

often sticky!

If both the mass and speed of an object are doubled, its momentum

quadrupled

The amount of gravitational potential energy possessed by an elevated object is...

quail to the work done against gravity in raising it

the greater change in momentum occurs for the ....

same for both

the greater impulse (bug/bus) acts on the

same for both

Quantity of work done is equal to

the amount of force x the distance moved in the direction in which the force acts

It is correct to say that impulse is equal to

the change in momentum

A grasshopper has a collision with a window shield of a speeding bus. The largest change in momentum is for

the change is the same for both

The recoil momentum of a gun that kicks is what compared to the momentum of the bullet it fires

the same as

a fast moving bus and a slow flying bug have a head-on collision. The unfortunate bug splatter over the windshield. During the collision the greater force acts on the

the same for both

The difference between impulse and impact force involves the

time the force act

A heavy truck and a small car move down the street at the same speed. Which has the greater momentum

truck

Two cars, one twice as heavy as the other, move down a hill at the same speed. Compared to the lighter car, the momentum of the heavier car is....

twice as much

An object is raised above the ground gaining a certain amount of potential energy. If the same object is raised twice as high, it gains

twice as much potential energy

A 1000kg car and a 2000g car are hoisted the same distance in a gas station. Raising the more massive car requires

twice as much work

If you push an object twice as far while applying the same force, you do

twice as much work

If you do work on an object, in half the time, your power outpus is

twice the usual out put