phys 107 test 2 test and quizzes

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5 -kg bowling ball that is initially at rest on a frictionless surface. The speed of the putty thereafter is

1/6 m/s.

a jack system will increase the potential energy of a heavy load by 400 J and generate 600 J of heat with a work input of 1000 J. The efficiency of the jack system is

40% useful w(input) useful w(output) heat is not useful 400/1000

A jack system will increase the potential energy of a heavy load by 400 J and generate 600 J of heat with a work input of 1000 J. The efficiency of the jack system is

40%.

A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it were traveling at 150 km/hr?

180 m

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.

If you need to tighten a bolt with 80 Nm of torque using a wrench with a handle that is 25 cm from the axis of the bolt, how much force do you need to apply when turning the wrench?

320 N . d = 25 cm T= 80 Nm F= ? T=fxL.A . F=T/LA 80/25 = 80 divided by 1/4

a 2-kg mass is held 4m above ground. what is the approx potential energy of the mass with respect to the ground?

80 J m= 2kg h=4m PEg=? PE=mgh 2x4x10m/s = 80 j

A longer cannon barrel is advantageous because it increases

A impulse delivered to the ball by allowing the force to be applied for a longer time. C the ballʹs momentum by increasing its velocity

How can you increase the angular momentum of a ball spinning on a string?

A increase the length of the string B spin the ball faster

A woman alleviates her back pain in the fifth month of pregnancy by wearing a backpack instead of carrying a purse. When the pain resurfaces in the ninth month of pregnancy, she can reduce the back pain once again by

A walking in snowshoes. B adding a few books to her backpack. C hanging the backpack from the end of a stick carried over her shoulder. D delivering the baby.

A large heavy truck and a small baby carriage roll down a hill. Neglecting friction, at the bottom of the hill, the baby carriage will have a greater

NONE A speed. B acceleration. C momentum.

Which jar will roll down an incline in the shortest time, an empty one or one filled with peanut butter?

The filled jar

The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is

above a place of support

a simple lever, properly arranged is capable of multiplying work input

always false

A hydraulic press, like a wheel and axle, is capable of multiplying force input.

always true

Acrobat Bart at the circus drops vertically onto the end of a see-saw, with his partner Art equidistant from the fulcrum at the other end. Art is propelled straight upward a distance twice that of Bart's dropping distance. Neglecting inefficiencies we see

art has half the mass of bart Mbgh=Mag2h Mb=2Ma

In class, I laid on a bed of nails with cinder blocks stacked on top of me. When Thomas struck the blocks with the sledgehammer, the kinetic energy of the hammer went into

cinder block??

When a twirling ice skater brings her arms inward, her angular momentum

decreases

When a twirling ice skater brings her arms inward, her rotational inertia

decreases.

a car travels in a circle with constant speed. the net force on the car is

directed towards the center of the curve

A car travels in a circle with constant speed. The net force on the car is

directed towards the center of the curve.

Two pool balls, each moving at 2 m/s, roll toward each other and collide. Suppose after bouncing apart, each moves at 4 m/s. This collision violates conservation of

energy

when a car is braked to a stop, its kinetic energy is transformed to

heat

When a car is braked to a stop, its kinetic energy is transformed to

heat.

an upright broom is easier to balance when the heavier end is

highest, farthest from your hand

a longer cannon barrel is advantageous because it increases

impulse delivered to the ball by allowing the force to be applied for a longer time & the ball's momentum by increasing its velocity

how can you increase the angular momentum of a ball . spinning on astring

increase length, spin ball faster

A heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the heavy truck will have greater

kinetic energy.

a heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the heavy truck will have greater

momentum

a heavy truck and a light truck roll down a hill. neglecting friction, at the bottom of the hill, the light truck will have less

momentum and kinetic energy

doing twice the work on an object in four times the usual time requires

one half the usual power p=w/t 2wo/4to = 1/2 P(original)

your pet hamster sits on a spinning record player. if the angular speed of the record player doubles and he moves to a point twice as far from the center, then his linear speed

quadroples

If you do twice the usual work on an object in half the usual time, your power output is

quadruple the usual power output.

Your pet hamster sits on a spinning record player. If the angular speed of the record player doubles and he moves to a point half as far from the center, then his linear speed

remains the same.

a ring, a disk, and a solid sphere begin rolling down a hill together. the one to reach the bottom last is the

ring

Centrifugal force are an apparent reality to observers in a reference frame that is

rotating

Centrifugal forces are an apparent reality to observers in a reference frame that is

rotating.

which requires the most amount of work by the brakes of a car?

slowing down from 100 km/h to 70 km/h w= change in KE 1/2(m)(100)^2 greater than other options fdl

the center of mass of a human body is located at a point

that changes as a person bends ober

The center of mass of a human body is located at a point

that changes as a person bends over.

Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr?

the 60 km/hr car

which has a greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr

the 60 km/hr car

When trying to turn a stubborn screw, you can generate twice as much torque by switching to a screwdriver with a handle that is

twice as wide

Two 1 kg billiard balls roll toward each other, each moving with speed 10 m/s. What is the combined momentum of the two balls?

0 kg m/s

a 1 kg glider and a 3 kg glider both slide toward each other at 2 m/s on an air track. They collide and stick. The combined mass moves at

1 m/s M1=3kg M2=1kg Vf= ? Vi1=2m/s Vi2=-2m/s Conservation of momentum Σ(mv)i=Σ(mv)f 3kg(2m/s)+(1kg)(-2m/s)=4kgVf 1m/s=Vf

A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/s. The recoil velocity of the rifle is about

1 m/s. Mr=2 kg Mb= 0.01 kg Vb= 200 m/s Vr=? Σ(mv)i=Σ(mv)f -MbVb=MrVr MbVb/Mr=Vr (0.01)(200)/2=2/2=-1m/s

two billard balls of the same mass roll straight toward each other. The first has a velocity of + 5 m/s and . the second has a velocity of -3 m/s. After colliding the first ball has a velocity of

- 3 m/s switch velocities

Two billiard balls of the same mass roll straight toward each other. The first has a velocity of +5 m/s and the second has a velocity of -3 m/s. After colliding, the first ball has a velocity of

-3 m/s.

How much work is done on a crate as it slides 10 m across the floor at a constant velocity of 2 m/s?

0 J

to do 10 J of work pushing a crate using 2 N of force, you will need to push the crate

5m work= 10j force= 2n d=? W=Fd d=w/f 10/2 = 5 m

how long will it take to stop . a 1500 kg car moving at 20 m/s with a braking force of 6000 . N

5s m=1500 kg F=-6000N Vi=20m/s t=? Vf= 0m/s Impulse M(Vf-Vi) F = t (1500kg)(0m/s-20m/s) -6000N =5s