Physical Science Exam 2 (incorrect answers in parentheses)

If an astronaut whose total mass is 100 kg ejects .1 kg of gas at a speed of 50 m/s from her propulsion pistol, her recoil speed is...

.05 m/s (50, 5, .5)

Two billiard balls having the same mass roll toward each other, moving at the same speed. What's the combined momentum of the two balls?

0 kg m/s (10 kg m/s, more info needed)

An arrow shot horizontally hits the ground in 1.5 s. If it had been fired with 2x the speed in the same direction, it would have hit the ground in...

1.5 s ( less than 1.5, more than 1.5, cannot be determined)

A car moves 4x as fast as another identical car. Compared to the slower car, the faster car has...

16x the KE (4x, 8x, 12x, cannot be determined)

A ball player wised to determine pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The player sees the ball land 20 m downrange. What is the player's pitching speed?

20 m/s (4, 5, 100)

Exert 3 N for a distance of 1 m in 1 s and you deliver a power of

3 W (1, 2, 1/3, 5)

A bowling ball is thrown horizontally from the top of a cliff. One second after it has left our hand its vertical distance below the cliff is...

5 m (10, 15, 20)

A 5 kg fish swimming at a speed of 1 m/s swallows and absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is...

5/6 m/s (1/2, 2/5, 6/5, 1)

Which one of the following has the largest momentum relative to the earth?

a pickup truck speeding along a highway b/c it has the best combination of large mass and high velocity (a tightrope walker crossing Niagara Falls, a Mack truck parked in a parking lot, the science building on campus, a dog running down the street)

When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, the time of impact is about 10x more than for a stiff-legged landing. In this way the average force your body experiences is reduced by...

about 10x (less than 10x, more than 10x)

A karate expert executes a swift blow and severs a cement block with her bare hand. The magnitude is the same for the...

all of these (impulse on the block and the hand, force on the block and the hand, time of impact on the block and the hand, none)

A heavy pile driver starting from rest falls on a pile with a force that depends on the...

all of these (original height of the driver, original potential energy of the driver, distance the pile falls, none)

The force of an apple hitting the ground depends on...

all of these (the speed of the apple just before it hits, the time of impact with the ground, whether or not the apple bounces)

A cannonball fired from a cannon begins to fall...

as soon as it leaves the barrel ( after air friction reduces its speed, neither of these)

The earth's gravitational field extends...

both inside and outside the earth and throughout the entire universe (only above and beyond the earth's surface and cancels inside the earth, neither of these)

If you push for an hour against a stationary wall, you do no work ...

both on the wall AND at all (on the wall, at all, none)

You're driving down the highway and a bug splatters into your windshield. Which undergoes the greater change in momentum?

both the same (the bug, your car)

A cannon recoils from firing a cannonball. The speed of the cannon's recoil is small because the...

cannon has more mass than the ball (force against the cannon is smaller than against the ball, momentum is mainly concentrated in the ball, momentum of the cannon is smaller)

The force that accelerates a rocket in outer space is exerted on the rocket by the...

exhaust gases (engines, wings, atmospheric pressure, none)

Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is...

greater than that of the apple only if the apple bounces (negligible compared to the apple's momentum, greater than the apple in all cases, none)

A clerk can lift containers a vertical distance of 1 m or can roll them up a 2 m long ramp to the same elevation. With the ramp, the applied force required is about...

half as much (twice as much, the same)

A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has half as much mass, its momentum is...

halved (zero, doubled, quartered, unchanged)

A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the recoiling gun..

if the mass of the bullet equals the mass of the gun (b/c momentum is conserved, b/c velocity is conserved, b/c both velocity and momentum are conserved, none)

A cannonball shot from a cannon with a long barrel will have a greater muzzle velocity because the cannonball receives a greater...

impulse (force, both, none)

If the radious of the erth somehow decreased with no change in mass, your weight would...

increase (not change, decrease)

Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has...

increased time of impact AND decreased impact force (increased time of impact, decreased impulse, decreased impact force, A and B)

According to Newton, he greater the distance between masses of interacting objects, the...

less the gravitational force (more, same)

A moving object on which no forces are acting will continue to move with constant...

momentum (acceleration, impulse, all, none)

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

momentum (speed, acceleration, all, none)

An object htat has kinetic energy must be...

moving (falling, at an elevated position, at rest, none)

A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of...

power (energy, both, none)

It is correct to say that impulse is equal to...

the change in momentum (momentum, the force times the distance the force acts)

No work is done by gravity on a bowling ball that rolls along a bowling alley because...

the force on the ball is at right angles to the ball;s motion ( no force acts on the balll, no distance is covered by the ball, no potential energy is being converted to kinetic energy, its kinetic energy remains constant.

A 50 kg sack is lifted 2 m in the same time as a 25 kg sack is lifted 4 m. The power expended in raising the 50 kg sack compared to the power used to lift the 25 kg sack is...

the same (4x as much, 2x as much, half as much, 1/4 as much)

Suppose a gun were made of a strong but light material. Suppose also that the pellet is more massive than the gun itself. For such a weapon...

the target would be safer than the shooter (recoil problems would be lessened, conservation of energy would not hold, conservation of momentum would not hold, both conservation of energy and momentum would not hold)

The difference between impulse and impact force involves the...

time the force acts (distance the force acts, difference between acceleration and velocity, mass and its effect on resisting a change in momentum)

An object is raised above the ground gaining a certain amount of potential energy. If the same object is raised twice as high, it gains...

twice as much potential energy (four times, half as much, the same amount, none)

If you push an object twice as far while applying the same force, you do...

twice as much work (four times as much, the same amount, half as much, 1/4 as much)

Consider driving into a massive concrete wall with no "give", versus having a head-on collision at the same speed with an identical car moving toward you with the same speed. It would be more damaging to hit the...

wall (car, both the same, no answer text provided)

A 1-N apple falls to the ground. It hits the ground with an impact force of about...

Not enough info (1 N, 2 N, 4 N, 9.8 N)

What prevents satellites such as the space shuttle from falling?

Nothing; they continually fall around the earth (gravity, centripetal force, centrifugal force, the absence of air drag)

The conservation of momentum is most closely related to...

Newton's Third Law (his first law, his second law)

A car traveling along the highway needs a cerain amount of force exerted on it to stop. More stopping force may be required when the car has..

all of these (more mass, more momentum, less stopping distance, none)

The power expended when a barbell is raised 2.0 m in 2 s is...

dependent on the mass of the barbell (1 W, 4 W, 8 W)

A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of speed because it...

is not acted on my any horizontal forces (is not acted on by any forces, has no vertical component of speed to begin with, ht e net fore acting on it is zero, none)

An object that has potential energy may have this energy because of its...

location (speed, acceleration, momentum, none of these)

When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a ...

long time (short time, same either way)

In order to catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion upon impact. Doing this reduces the force of impact on the player's hand principally because the...

time of impact is increased (force of impact is reduced, relative velocity is less, time of impact is decreased, none)