# Physics

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Galileo

10N

3000N

### The two measurements necessary for calculating average speed are

distance and time

20 km/h

zero

hypotheses

theory

### An object in mechanical equilibrium is an object

at rest
moving with constant velocity
having no acceleration

### A truck is moving at constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor below. The rock hits the floor

exactly below the midpoint of the ceiling

9.8 N

800 seconds

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

the change in momentum

Newton's 2nd law

Newton's 3rd law

### A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the

rifle has much more mass than the bullet

### Suppose that a tiny gun made of a strong but very light material fires a bullet that is more massive than the gun itself. For such a weapon

the target would be safer than the shooter

momentum

### 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. Doing this reduces the force of impact on the player's hand principally because the

time of impact is increased

### Padded dashboards in cars are safer in an accident than non-padded ones because an occupant hitting the dash has

increased time of impact

### The force on an apple hitting the ground depends upon

the speed of the apple just before it hits.
the time of impact with the ground.
whether or not the apple bounces.

3m/s
p = mv
p/m= v
v =12/4
= 3m/s

### A karate expert executes a swift blow and breaks a cement block with her bare hand. The magnitude of the force experienced by her hand is

identical to the force applied

0

1W

decreased

2 m/s

nearest the rim

rotation

### On a balanced seesaw, a boy three times as heavy as his partner sits

1/3 the distance from the fulcrum

2

center of mass

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

above a place of support

increases

### For a system in mechanical equilibrium the resultant forces and torques

must both be zero.

1kg

### Suppose you roll a ball off a tabletop. Will the time to hit the floor depend on the speed of the ball?

No (because the vertical velocity is independent of the horizontal)

### Suppose you roll a ball off a tabletop. Will the time to hit the floor depend on the speed of the ball?

Yes. (because the horizontal component of velocity combined with the vertical component results in a greater speed. That is why the ball travels a longer distance in the same amount of time)

### If you toss a ball vertically upward in a uniformly moving train, it returns to its starting place. Will it do the same if the train is accelerating?

No (since the train is accelerating and the ball is moving at a constant velocity.)

yes

### Which planets have a more than one Earth year period, planets nearer or farther from the sun?

planets farther form the sun

gravity

### Mars has about 1/9 the mass of Earth. If Mars were somehow positioned into the same orbit as Earth's, how would its time to circle the Sun compare with Earth's?

it would be the same

increases

### In an accidental explosion, a satellite breaks in half while in circular orbit about Earth. One half is brought momentarily to rest. What is the fate of half brought to rest? What happens to the other half?

the half brought to rest falls to Earth and the other half's velocity doubles

### Science is a body of knowledge that

describes order in nature
is an ongoing activity of humans
condenses knowledge into testable laws

may change

experiment

### Acceleration equals

velocity and time

### If no external forces are acting on a moving object it will

continue moving at the same velocity

increases

zero

20 m/s

### If an object moves with constant acceleration its velocity must

change by the same amount each second

800 N

moon

Newtons

10 times as much

### An astronaut, floating alone in outer space throws a baseball. If the ball floats away at a peed of 20 m /s the astronaut will

move in the opposite direction but at a lower speed

### If a monkey floating in outer space throws hi hat away, the hat and the monkey will both

move away from each other but at different speeds

1/3 m/s

### Which requires the most amount of work by the brakes of car

slowing down from 100 km/h to 70 km/h

### According to Newton, doubling the distance between two interacting objects

divides by 4 the gravitational force between them

500 N

### Inside a freely falling elevator, there would be no

apparent weight for you

40 N

Earth

### The amount of gravitational force that acts on the space shuttle while in orbit is

almost as much as the shuttle's weight on the Earth's surface

5m

atmosphere

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