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
