Physics final

An object of mass 1 kg that is moving in a straight line on a level surface slows down from 2 m/s to rest. What is the net work done on the object?

-2 Joules

What is meant by the term vector resolution?

A vector can be broken into two components at right angles that add together to make the original vector.

Why doesn't the Leaning Tower of Pisa topple over?

A vertical line through the center of gravity passes inside its support base.

Which of the following statements is true about a falling object that has reached terminal velocity?

Air resistance and weight are equal and opposite forces.

What does it mean to say something is in mechanical equilibrium?

An object in mechanical equilibrium experiences a zero net force.

Which of the following statements are TRUE about momentum?

An object's momentum is equal to the product of its mass and its velocity. Momentum is a vector quantity

What happens to the water pressure at the bottom of a geyser when some of the water above gushes out? What is the result?

As water rushes out, the pressure on the remaining water is reduced, so the water boils.

Why do you feel uncomfortably warm on a hot and humid day?

Cooling sweat does not evaporate well in humid air.

What was the greatest discovery by Galileo during his inclined-plane experiments?

He discovered that a ball rolling down an incline and onto a horizontal surface would roll indefinitely.

Why does increasing the temperature of a solid make it melt?

Increasing the temperature increases molecular vibrations until attractive forces can no longer hold the molecules in one place

A block of mass 2 kg is acted upon by two forces: 3N (directed to the left) and 4N (directed to the right). What can you say about the block's motion?

It could be moving to the left, moving to the right, or be instantaneously at rest.

If you punch holes in the side of a container filled with water, in what direction does the water initially flow outward from the container?

It flows straight out, perpendicular to the wall.

What happens to the kinetic energy of a moving object if the net work done is positive?

It increases.

Is it easier for a circus performer to balance a long rod held vertically with people hanging off the other end, or the same long rod without the people at the other end, and why?

It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is greater.

Is it easier to balance a long rod with a mass attached to it when the mass is closer to your hand or when the mass is farther away?

It is easier when the mass is farther from your hand.

What is the force of friction acting on a shoe at rest on an incline compared with the resultant of the vectors mg and N?

It is equal and opposite.

When an object is thrown upward, how much speed does it lose each second (ignoring air resistance)?

It loses 10 m/s of speed each second until it reaches the high point, then it gains 10 m/s each second.

Object A has a mass and a speed , object B has a mass and a speed , and object C has a mass and a speed . Which of the following is/are TRUE?

Object B has the greatest magnitude of momentum. Object A and object C have the same magnitude of momentum.

Why does warm, moist air form clouds when it rises?

Rising air expands and cools. Water drops condense when moist air cools.

What is sublimation? Is it a heating or cooling process?

Sublimation is when the fastest molecules at the surface of a solid have escape velocity and leave to become a gas. It leaves behind the slower, cooler molecules.

A typical bullet has a mass of about 0.05 kg and has an initial speed (upon leaving the barrel of the rifle) of about 1,000 m/s. How fast should a medium-sized car (~1,000-kg of mass) be moving in order to have the same momentum?

The car should be moving about 0.05 m/s

Two identical train cars are on the same track. The first train car is moving with a speed of 10 m/s toward the stationary second train car. If they get hooked together upon contact, how fast will the newly connected trains be moving?

The connected trains will be moving 5 m/s.

An object is submerged under water. Suppose you increase the height of the object WITHOUT changing its depth under water. What will happen to the force due to pressure on the bottom of the object?

The force due to pressure on the bottom of the object will increase.

If you push on a crate with a horizontal force of 100 N and it slides at constant velocity, what is the magnitude and direction of the frictional force acting on the crate?

The frictional force on the crate is 100 N opposite the direction of motion.

The large piston of a hydraulic lift has an area twice the area of the small piston. In comparison to a force applied on the small piston, what would the force exerted by the large piston be?

The large piston would have double the force.

Why doesn't a heavy object accelerate more than a light object when both are freely falling?

The ratio of the weight to mass is the same for all objects in the same locality.

While goofing off at the ice skating rink, a student takes off her shoes and places each of them on the ice. Her friend, a hockey player, then shoots a hockey puck at each shoe. The first puck immediately comes to rest after it collides with the left shoe. The second puck rebounds after it collides with the right shoe. If each hockey puck has the same incoming speed, which shoe has greater speed after the collision?

The right shoe

When you cut a broom right through the center of gravity, how do the weights of the two sides of the broom compare?

The shorter side, where the bristles of the broom are, has a greater weight than the handle.

If a constant net force is applied to an object, which of the following statements is/are true? Select all that apply.

The velocity of the object changes linearly. The object has a constant acceleration.

As a boxer hits the bag, the bag hits back at the boxer. Which force happens first?

They act at the same time

What is the main difference between speed and velocity?

Velocity includes a direction, but speed does not.

Which varies with location, mass or weight?

Weight varies with location, but mass does not.

If a car moves with a constant velocity, does it also move with a constant speed?

Yes, because constant velocity requires constant speed in the same direction.

A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?

Yes, the bowling ball is in equilibrium because ΣF = 0.

Earth pulls down on you with a gravitational force that you call your weight. Do you pull up on Earth with the same amount of force?

Yes, you pull up on Earth with the same force

When you stand at rest on a bathroom scale, how does your weight compare with the support force from the scale?

Your weight is equal in magnitude and opposite in direction to the support force from the scale.

Changes of phase most always require _________.

a transfer of energy

Galileo discovered that when air resistance can be neglected, all objects fall with the same ______.

acceleration

Force vector components for a sled pulled horizontally by a rope at an upward angle _______.

are normally at right angles to each other

To double the rotational speed the centripetal force must _______.

be four times larger

Boiling is evaporation that mainly occurs _________.

below the surface and throughout water

When Monkey Mo dangles by a rope and pulls on his cage, each at different angle from the vertical, the rope tension will be greater than _______.

both his weight and the pull on his cage

How can you use a graph of velocity versus time to estimate the acceleration of a ball?

by estimating the value of the slope of the graph

When traveling three times as fast your kinetic energy is increased _______.

by nine times

The pressure increases on a block resting on a table when you increase the __________.

downward force on the block

When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______.

equal and opposite to the momentum of the fired cannonball

The buoyant force on a floating object is __________.

equal to the object's weight

The torque exerted by a crowbar on an object increases with increased _______.

force and leverage distance

When your foot stands on a tile floor, thermal energy always flows _________.

from either your foot or the tile, depending on the temperature of the tile

Evaporation is a change of phase _________.

from liquid to gas

Water pressure in a lake is ____________.

greater at the bottom

The tangential speed on the outer edge of a rotating carousel is _______.

greater than toward the center

Follow through is important in golf because it results in a greater _______.

impulse on the ball

A scuba diver is planning to dive to the same depth in the open ocean and in a deep lake. Considering that salt water is denser that fresh water, where would the diver feel more pressure?

in the ocean

Rotational inertia of an object rotating about an axis becomes greater with _______.

increased mass and increased distance to mass concentration

A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be __________.

moving with a constant nonzero acceleration

A car drives up a steeply inclined ramp. The work done on the car by the Earth's gravitational force is ____.

negative

An object having the same density as water will __________.

neither sink nor float in water

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____.

the object's final speed was the same as its initial speed

When a cue ball strikes an 8 ball head-on in a game of pool, the cue ball _______.

transfers its momentum to the 8 ball

When one does four the work in twice the time, the power expended is _______.

twice as much

When you lift the load twice as high, in half the time, the increase in potential energy is _______.

twice as much

What explains the dramatically different magnitudes of accelerations that result when a mosquito collides head on with a moving truck?

unequal masses of the bus and the mosquito

When a falling firecracker explodes, the momenta of its pieces _______.

vectorially add up to equal the initial momentum of the firecracker

Whenever a (non-zero) net force acts on an object, there is a change in the object's _________.

velocity

Most energy transfer occurs when 1 gram of H2O changes from _________.

water into steam

When two vehicles collide, momentum is conserved _______.

whether the collision is elastic or inelastic

A spacecraft moves around Earth in a circular orbit with a constant radius. How much work is done by the gravitational force on the spacecraft during one revolution?

zero

While you are in a bus that moves at 100 km/h, you walk from the back to the front at 10 km/h. What is your speed relative to the road outside?

110 kph

A ball freely falling at 3 m/s will in the next second have a speed of ______.

13 m/s

If an object suspended by a scale shows a weight of 8 N in air and 6 N when submerged in water, the buoyant force on the submerged object is __________.

2 N

While you are sitting in a park, you notice a bus moving at 3 m/s to your right and a passenger that starts walking to the back of the bus but who seems to stay at the same position in front of you. What is the velocity of the passenger respect to the bus driver?

3 m/s to your left

In its first second of free fall, a dropped softball will fall a vertical distance of ______.

5 m

A container with a mass of 5 kg is lifted to a height of 10 m. How much work is done by the gravitational force?

500 Joules

A medium size apple weighs 2 N and sits on an area of about 4 cm2 (0.0004 m2 ). Determine the pressure that the apple exerts on the surface.

5000 Pa

What did Galileo discover in his legendary experiment on the Leaning Tower of Pisa?

Galileo found that a heavier stone does not fall significantly faster than a lighter one.

A loaded ship arrives at the first freshwater lock of the Panama Canal, will it float higher or lower than in the open ocean?

It will float lower.

When one immerses an object in water, how does the loss of weight of the object compare with the buoyant force of the water?

Loss of weight is equal to the buoyant force.

How does Newton's first law of motion relate to Galileo's concept of inertia?

Newton refined Galileo's concept of inertia and made it his first law of motion.

What is the acceleration of a falling object that has reached its terminal velocity?

The acceleration is 0.

When a rifle is fired, how does the magnitude of acceleration of the rifle compare with the magnitude of acceleration of the bullet, and why?

The acceleration of the rifle is smaller than the acceleration of the bullet. They experience the same magnitude of force, but the mass of the rifle is greater, and so the rifle will experience a smaller acceleration than the bullet.

A book and a flat piece of paper were dropped together from the same height, and one object hits the ground before the other. Why does that object hit the ground first?

The heavier object--the book--hits the ground first because the other, lighter, object is more influenced by air resistance.

Describe the velocity and acceleration vectors of a projectile that is launched vertically up upon reaching its maximum height.

The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and the forces are in the opposite direction, because for every action there is an equal and opposite reaction.

A small car and a large truck have a head-on collision. Which of the following statements is true?

The magnitudes of both forces are the same.

An object at rest cannot remain at rest unless which of the following holds?

The net force acting on it is zero.

How does the pressure exerted by bubbles in the water compare with the atmospheric pressure when the temperature of water in an open pressure cooker is below 100 ∘ C and when it equals 100 ∘ C?

The pressure exerted by the bubbles is less than the atmospheric pressure below 100 C and equals the atmospheric pressure at 100 ∘ C.

A speedometer normally measures ______.

instantaneous speed

The rotational speed of every point of a rotating rigid object _______.

is the same

A ruler is in equilibrium on the tip of your finger only if __________.

net torque and net force are zero

A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is

none of the answers are correct

A pair of wires support a heavy painting. Tension in the wires is greater when they are

not vertical

The direction of the force of friction on a sliding crate is _______.

opposite to the direction of sliding

Boiling can occur in cold water when _________.

pressure is sufficiently lowered

The purpose of a pressure cooker is to _________.

prevent cooling from occurring

If the speed of a car increases, the friction force between the road and the tires _______.

remains constant

When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.

remains the same

A stone of volume V submerged in water displaces the _________.

same volume of water

The work that is done when twice the load is lifted one-half the distance is _______.

the same

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____.

the same magnitude and sign

A solid sphere and a hollow sphere (spherical shell) of the same mass and same radius rotate with the same amount of kinetic energy. Which one is rotating faster?

the solid sphere