Physics Exam 4

G.P.E.

Gravitational Potential Energy (mgh)u

Power=

Work done/time interval

If a turntable's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will

double

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

A collision where both momentum and kinetic energy are conserved is an

elastic collision

An earth satellite is simply a projectile

freely falling around the Earth

According to Newton, the greater the masses of the interacting objects, the

greater the gravitational force between them

The direction of a gravitational field is

in the same direction as the gravitational attraction

If the mass of the Earth somehow increased with no change in radius, your weight would

increase also

Two objects move toward each other because of gravity. As the objects get closer and closer, the gravitational force between them

increases

When a twirling ice skater brings her arm inward, her rotational speed

increases

Equation for inelastic

m1v1i+m2v2i=(m1+m2)VF

Equation for elastic

m1v1i+m2v2i=m1v1f+m2v2f

An object that has kinetic energy must be

moving

Horses that move with the fastest linear speed on a merry-go round are located

near the outside

An industrial flywheel has a greater rotational inertia when most of its mass is

nearest the rim

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity

remains unchanged

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the

rifle has much more mass than the bullet

A torque acting on an object tends to produce

rotation

A black hole is

simply the remains of a giant star that has undergone gravitational collapse

Inelastic does what

sticks together same velocity

A ball rolling down an incline has its maximum kinetic energy at

the bottom

A person weighs less at the equator than at the poles. The main reason for this has to do with

the spin of the earth

It is correct to say that impulse is equal to

the change in momentum it produces

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of

1 kg m/s (m1v1i+m2v2i= (m1+m2)vf) (1)(1) + (5)(0)=1

On a balanced seesaw, a boy three times as heavy as his partner sits

1/3 the distance from the fulcrum

Do 100 J of work in 50 s and your power output is

2 W (w/change in time)

Suppose the circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second when you are riding the bicycle, then your speed will be

2 m/s

A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed?

3 m/s

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy that

40 J

An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be

40 N

A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks.

B (up and to the right)

Energy conservation

Ei=Ef

If the above ball comes to rest in the catcher's mitt in .085 seconds, how much force does the ball apply on the catcher's mitt? (impulse-momentum theorem)

I=Fxt I=Pf-Pi I=0-9.43 I=-9.43 Fxt=-9.43 F(.085)/.085=-9.43/.085 F=-110.9 N

Equation for impulse

I=Fxt I=change in P

Energy is measured in

Joules

Equation for kinetic energy

K.E.=1/2mv2 (massxspeed)2

Equation for momentum

P=mv

A .230 kg baseball is thrown with a speed of 41 m/s. What is the ball's momentum?

P=mv P= (.230)(41) P=9.43 kgm/s

A 9.0 kg bowling ball races down the lane at 15 m/s before striking a bowling pin (at rest) with a mass of .85 kg. If the .85 kg pin bounces backward with a velocity of 45 m/s, what is the velocity of the bowling ball after the collision?

P=mv m1v1i+m2v2i=m1v1F+m2v2F (9.0)(15)+(.85)(0)=9v+(.85)(45) 135+0=9v+38.25 135=9v+38.25 -38.25=-38.25 96.75/9=9v/9 v=n10.75 m/s

A 50.0 N seesaw supports two people who weigh 455 N and 525 N. The fulcrum is under the CG of the board. The 525 N person is 1.50 m from the center. Where does the smaller person sit so the seesaw is balanced?

T=(525)(1.50) T=787.5 Nm TL=TR FLrL=Frrr 787.5=455x 787.5/455=455x/455 1.73 m=x

Earth satellites are typically more than 100 km high so as to be above the Earth's

atmosphere

Elastic does what

bounce off different velocities

A coin and a ring roll down an incline starting at the same time. The one to reach the bottom first will be the

coin

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its vertical component of velocity

decreases

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

twice as much work