Phys 1415 chapter 3
A diver who weighs 500 N steps off a diving board 10m above the water hits the water with kinetic energy of
5000j
A 5000kg freight car crashes into a 10000kg freight car at rest. They couple upon collision and move with a speed of 2m/s. What was the initial speed of the 5000kg freight car?
6m/s
A model airplane moves twice as fast as another identical model airplane. Compared to the kinetic energy of the faster airplane is
Four times as much
Which of these equations best explains the usefulness of automobile airbags?
Ft =/_\(mv)
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force to stop the car the force needed to stop the truck is
Greater
When a non hybrid car brakes to a stop its kinetic energy transforms to
Heat
The speed of a bullet fired from a gun will be about the same as the speed of the recoiling gun
If the masses of the bullet and gun are equal
When a 100kg astronaut ejects 0.1kg of gas at a speed of 50 m/s from her propulsion pistol, her recoil speed is
0.05m/s
A 30kg girl and a 25kg boy face each other on friction free roller blades. The girl pushes the boy who moves away at a speed of 1.0 m/s. The girls speed is
0.83 m/s
Two billiard balls having the same mass roll toward each other at the same speed. What is the net momentum of the two ball system?
0kg m/s
Two identical gliders slid toward each other on and air track. One glider moves at 1 m/s and the other glider moves at 2 m/s. They collide and stick. The combined gliders move at
1/2 m/s
A 1kg glider and a 2kg glider both slide toward each other at 1 m/s on an air track. They collide a stick. The combined gliders move at
1/3m/s
A 1kg chunk of putty moving at 1 m/s collides with and sticks to a 5kg bowling ball that is initially at rest in space. The bowling ball and putty are then set in motion with a speed of
1/6 m/s
Consider gliders that slide friction free along a horizontal air track. Glider a has a mass of 1kg a speed of 1 m/s and collides itch glider b which has a mass of 5 kg and is at rest if they stick upon collision the speed the combined gliders will be
1/6 m/s
A 5kg fish swimming at a speed of 1 m/s swallows an absent minded 1kg fish swimming toward it at 4m/s. The speed of the larger fish after lunch is
1/6m/s
A kg ball has the same speed as a 10kg ball. Compared with the 1kg ball the 10kg ball has
10 times as much momentum
A machine puts out 100 w of power for every 1000w put into it. The efficiency of the. Machine is
10%
A ball is moving at 4 m/s and has a momentum of 48 kg m/s. What is the ball mass?
12kg
A 1kg chunk of putty moving at 1 m/s collides with and sticks to a 5kg bowling ball that is initially at rest. The bowling ball and putty move with a momentum of
1kg m/s
A rifle of mass 2kg is horizontally suspended by a pair of strings so that recoil can be measured. The rifles fires a bullet of mass 1/100kg at a speed of 200 m/s. The recoil velocity of the rifle is about
1m/s
Exert 1N for a distance of 1m in 1 s and you deliver a power of
1w
A 1000kg car moving at 10 m/s that brakes to a stop in 5s has an average braking force if
2000N
A 2500N pile driver ram falls 10m and drives a post 0.1 m into the ground. The average force on the post
250000N
A 2kg mass that weighs 20N has 40j of potential energy relative to the ground. What is the height?
2m
A 4kg ball has a momentum of 12kg m/s. What is the ball speed?
3 m/s
How much work is done on a 200kg crate that is hoisted 2m in a time of 4s?
4000J
A music console is pushed a distance of 2 m with the force of 20 N. The work done on the console
40j
A 5kg fish swimming at a speed of 1 m/s swallows an absent minded 1kg fish at rest. The speed of the larger fish after lunch is
5/6 m/s
A boxer punches a sheet of paper in midair from rest to a speed of 40 m/s in 0.05s. If the mass of the paper is 0.01kg the force of the punch on the paper is
8.0N
A 2kg mass weighs 20N and is held 4 m above the ground. It's potential energy relative to the ground is
80j
In the absence of external forces momentum is conserved in
Either and elastic or Inelastic collision
A machine cannot multiply
Energy
Padded dashboards in cars are safer in an accident than non padded ones because an occupant hitting the dash has
Both a and b
Which requires more work lifting 50 kg sack vertically 2 m or lifting a 25kg sack 4m
Both require the same amount of work
You're driving down the highway and a love bug spatters onto a windshield. Which undergoes the greater force of impact?
Both the same
Which of theses equations is most useful for solving a problem that ask for the distance a fast moving box slides across a post office floor and comes to a stop?
Fd=/_\mv^2
Whereas impulse involves the time that a force acts work involves the
Distance that a force acts
A billiard ball and a bowling ball have the same speed. Compared with the heavier bowling ball the lighter billiard ball has
Less momentum and less kinetic energy
An object in motion will continue in motion with
Momentum
If the running speed of fast Freda doubled what also doubled is her
Momentum
An object that has kinetic energy must be
Moving
A 0.5 kg blob of clay moving at 2.0 m/s slams into a 4.0 kg blob of clay at rest . The speed of the two blobs stuck together after colliding is about
None
A 1N apple falls to the ground. The apple hits the ground with a force of
Not enough information
If you push for and hour against a stationary wall you do no work
On the wall
The ultimate source of energy for wind power , fossil fuels and biomass is
Solar
The ultimate source of energy from fossil fuels is the
Sun
It is correct to say that impulse is equal to
The change in momentum
The most underlying feature of machines is
The conservation of energy
In order to catch a fast moving softball with your bare hands you extend your hand forward just before the catch and then let the ball ride backward with your hand doing the reduces the catching force because
Time to catch is increased
The most energy per unit mass can be extracted from
Uranium
