Test 2 PS

A wheelbarrow is an example of a

second class lever

The impulse-momentum relationship is a direct result of Newton's

second law

Which of the following objects exerts a gravitational force?

-- a bowling ball -- a book -- a feather

The concept of free-falling objects applies to

--apples --the moon --the planets

The density of air in the atmosphere varies with

--temperature. --altitude. --gaseous composition.

When you jump from an elevated position to the ground below, the force you experience when landing depends on

--the jumping height. --how much your knees bend. --the softness or hardness of the ground.

Gravitational potential energy depends on

--the mass of the object --height of the object --the acceleration due to gravity

The buoyant force that acts on a 1000-N boat is

1000 N

A 1-kg rubber ball and a 1-kg blob of putty drop on a floor from the same height. Which exerts greater force on the floor?

Ball because it bounces

An elephant on slippery ice shoots a peanut from its trunk in a horizontal direction. Which has the greater amount of momentum change—the elephant or the peanut?

Both the same.

The energy source for dry-rock geothermal power is

Earth's thermal energy

_____ is the ratio of useful work output to work input

Efficiency

A low-mass molecule and a high-mass molecule moving with the same kinetic energy have equal speeds

False

A main reason the Moon doesn't crash into Earth is because Earth gravity is very small at Moon's relatively large distance

False

An automobile and a skateboard moving at the same speed in the same direction have equal momenta.

False

An egg tossed into a sagging sheet rather than against a wall will not break because the momentum change is less for the sagging sheet

False

Earth and the Moon gravitationally attract each other, with Earth pulling harder on the Moon than Moon pulls on Earth

False

For a projectile, the horizontal component velocity is proportional to its vertical component of velocity.

False

For a satellite in an elliptical orbit around Earth, both gravitational force and speed remain unchanged everywhere

False

If gravitation between Earth and the Moon suddenly disappeared, the Moon would nevertheless continue circling Earth

False

The law of energy conservation does not apply to nuclear reactors

False

When a gymnast falls on a thick mat, both the impulse and force of fall is decreased.

False

When a skateboarder at rest tosses a ball horizontally, the speed of the tossed ball is equal to the speed of the recoiling skateboard.

False

When two lumps of equal mass clay have a head-on collision and come to rest, both momentum and kinetic energy are conserved

False

How does the total momentum of two objects before a collision compare with the total momentum after the collision?

It is the same.

What will happen to air bubbles in a narrowing pipe of moving water?

The air bubbles will get bigger

Airbags in cars reduce injuries by providing more time in which the momentum of an occupant changes, thereby reducing force

True

An apple falling from a tree and the Moon are both affected by the same source of gravity

True

A ball tossed straight up in the air has its maximum potential energy at the top of its path

True

A boxer rides with the punch so as to increase the time of contact with the opponent's glove, which lessens the force.

True

A cart traveling at the same speed on Moon's surface has just as much momentum as the same car at the same speed on Earth's surface.

True

A mountain lion and a rabbit running with the same kinetic energy have unequal speeds

True

A projectile is any object projected by any means that continues in motion

True

An explanation of the swinging-ball apparatus, wherein two balls released always results in two identical balls popping out, involves both the conservation of momentum and the conservation of energy

True

For a satellite in circular orbit around Earth, both gravitational force and speed remain unchanged everywhere

True

If you do 100 J of net work on a cart, its energy will increase by 100 J

True

In the absence of air drag, the vertical component of a projectile's motion continually changes

True

The gravitational force decreases between a pair of planets when they get farther apart

True

The higher the efficiency of a device, the less thermal energy is generated

True

The kinetic energy of a roller coaster is greater at lower elevations than at higher elevations

True

The potential energy of a roller coaster is greater at higher elevations than at lower elevations

True

Two shopping carts having a collision encounter the same amount of force regardless of mass.

True

When a rocket in space gives momentum to exhaust gases, the same amount of momentum is imparted on the rocket by the gases.

True

When a skateboarder at rest tosses a ball horizontally, the momentum of the tossed ball is equal to the momentum of the recoiling skateboard.

True

Is there a buoyant force acting on you at this minute?

Yes, but you don't feel it because of your much greater weight

The shape of a satellite's path when traveling at a constant speed is

a circle

A pair of tweezers is

a compound machine made of two third-class levers

Which is an example of projectile motion?

a dart thrown at a dart board

Which of the following has a momentum of zero?

a newspaper lying on a table

The magnitude of G indicates that gravity is

a relatively weak force

Which object does not have momentum?

a rock by the side of the road

A hot air balloon that hovers without motion displaces

a weight of air equal to its own weight

Which of the following is not a factor in calculating momentum?

acceleration

A first-class lever has the

fulcrum in the middle

Which of the following is a simple machine?

all of the above

In the absence of external forces, momentum is conserved in

both an elastic or an inelastic collision

Legend tells us that Newton realized that the idea of falling applies to

both apples and the moon

Archimedes' principle applies to fluids, which means it applies primarily to

both liquids and gases

When a falling object bounces as it hits the ground

both of these

Mechanical energy applies to

both potential and kinetic energy

A machine is a device that

can multiply and change the direction of an input force

The law of conservation of energy states that energy

cannot be created or destroyed

If air speed is greater along the top surface of the wing of an airplane, pressure of the moving air there is

decreased

When objects are moved further apart from each other, the force of gravity between them

decreases

When two trucks traveling in opposite directions pass each other, the air pressure between the trucks

decreases

Wind speeding up as it blows over the top of a peaked roof

decreases atmospheric pressure there

Water pressure at the bottom of a deep pond depends on the

depth of the pond

Whereas impulse involves force and time, work involves force and

distance

The gravitational force between two objects depends on masses of objects and

distance between objects

If you squeeze a balloon to half its volume, the air pressure in the balloon will be

doubled

Energy is conserved when an Earth satellite travels in a

either an elliptical or circular path

_____ is a measure of the ability to do work

energy

When a cannonball is shot from a cannon, the cannon recoils. Compared with the momentum given to the cannonball, the momentum of the recoiling cannon is ideally

equal and opposite

Buoyancy on a floating object

equals both weight and volume of fluid displaced

The density of a hovering balloon

equals the density of the surrounding air

What Newton discovered about gravity was that it

extends at least to the Sun and planets

Any object composed of iron will sink in water

false

As a fish swims deeper in a lake, water pressure on the fish remains relatively constant

false

Water pressure in home faucets is the same on high floors as it is on basement floors

false

When a stream of water gains speed, pressure within the water increase

false

When a stream of water gains speed, pressure within the water increases.

false

A satellite in elliptical orbit about Earth travels slowest when it moves

far from Earth

Impulse depends on

force and time

Orbital motion is a combination of

forward motion and free fall

Raising an auto in a service station increases its gravitational potential energy. Raising it four times as high increases its potential energy by

four times

When two identical cars, one traveling twice as fast as the other, brake to a stop with old-fashioned brakes, the faster car will skid

four times as far

A helium-filled balloon hovers in air. The pressure of the atmosphere against the bottom of the balloon must be

greater than pressure against the top

The buoyant force that acts on an object submerged in water is due to

greater water pressure on the bottom than on the top

The potential energy of a satellite in an elliptical orbit is

greatest at the apogee (farthest point)

The velocity of a satellite in an elliptical orbit is

greatest at the perigee (nearest point)

For a tossed ball, the component of velocity that remains constant without air drag is the

horizontal component

Astronauts "float" when inside an orbiting spaceship because they are

in free fall

A wedge is a modified

inclined plane

Consider a U-shaped tube filled with water with pistons at each end. When pressure is increased at one end of the tube, pressure at the other side will

increase by the same amount

When you stand on one foot rather than two feet, you

increase the pressure on the floor

Atmospheric pressure becomes less with

increasing altitude

Momentum is described as

inertia in motion

Pumice is a volcanic rock that floats in water. The density of pumice

is less than the density of water

When a moving bowling ball hits a pin, some of the ball's momentum

is transferred to the pin.

While standing on a skateboard at rest, you catch a horizontally-moving ball. Compared with the initial speed of the ball, the speed of you and the ball is

less

Lifting a car using a car jack is easier because it requires

less force

Bernoulli's principle says that when the speed of a fluid increases, there is

less pressure in the fluid

An object's momentum is determined by the object's

mass and velocity

The force of gravity between two objects depends on their

masses and distance apart

Newton imagined a cannonball fired horizontally from atop a mountain in the absence of air drag. He hypothesized that the cannonball would be an Earth satellite if its curved path

matched Earth's curvature

At the top of its arc, a thrown ball has _____ potential energy

maximum

Water from a fire hose knocks over a wooden shed. Compared with the pressure within the water, the water pressure against the shed is

more even though pressure within the fluid is less

One object has a greater density than another when it has

more mass per given volume

You feel less stopping force when falling into a net rather than a rigid surface because of

more time for momentum change

When you catch a fast-moving baseball with your bare hand, it's a good idea to

move your hand in the direction the ball is moving

An object with density equal to the density of the fluid in which it is immersed

neither sinks nor floats

The force of gravity between two planets depends on

none of these

The primary source of the sun's energy is

nuclear fusion

Atmospheric pressure is due to the weight

of the atmosphere

When a projectile achieves escape speed from Earth, it

outruns the influence of Earth's gravity, but is never beyond it

Which of the following is an example of mechanical energy?

potential energy

As a dropped penny falls toward the ground, _____ energy is converted to _____ energy

potential, kinetic

_____ is defined as the rate at which work is done

power

If a car comes to a full stop when hitting a haystack and hitting a stone wall, the change in momentum is greater for hitting the

same momentum change in both cases

The Moon remains in orbit while falling around the Earth due to its

tangential velocity

Most of the energy on earth ultimately comes from

the Sun

When a 1-kg cart on an air track bumps into another 1-kg cart and they stick, the momentum after sticking is

the same as before

The potential energy of a satellite in circular orbit is

the same everywhere

For a tossed ball, the component of velocity that changes with time even without air drag is

the vertical component

A ball rolling along a bowling alley maintains its speed because

there is no horizontal force acting on the ball

Levers are divided into _____ classes based on the location of the fulcrum and of the input and output forces.

three

In hitting something, follow-through is important. This increases the impulse by increasing the

time of contact

A helium-filled balloon that floats in air displaces its weight of air

true

As an air-filled balloon is pulled deeper and deeper in water, the volume of the balloon decreases and buoyant force on the balloon also decreases

true

If water pressure were the same at all depths, buoyant force wouldn't occur

true

The buoyant force on a floating boat equals the weight of the boat, and also the weight of water displaced by the boat.

true

You float higher in salt water compared with fresh water because you don't have to "sink" as far to displace your weight of denser salt water

true

When work is done twice as quickly, then the power expended is

twice

Raising a heavy load requires work. Raising it twice as high requires

twice the work

While a projectile moves horizontally with no change in motion, it moves vertically

under the influence of gravity

A completely submerged object always displaces its own

volume of fluid

When you say momentum is conserved, you mean that

without external impulses, a system's momentum remains the same before and after an interaction

When you try jumping from a rowboat to the dock, you may fall in the water because

you'll make the boat recoil and underestimate your jump.

When you jump from an elevated position to the ground below, the force you experience when landing does NOT depend on

your attitude about jumping