physics midterm chapter 4

Phil stands at rest with both feet on a scale that reads 500 N. After he gently lifts one foot, the scale reads

500N

A stone is thrown horizontally from the top of a cliff. One second after leaving your hand it drops a vertical distance of

5m

An astronaut lands on a planet that has the same mass as Earth but half the diameter. How does the astronaut's weight differ from that on Earth?

Astronaut has four times as much weight as on Earth.

A stone is thrown upward at an angle. Neglecting air resistance, what happens to the vertical component of its velocity along its trajectory?

At first it slows down, then reverses direction and speeds up.

Where do you weigh more—at sea level or atop one of the peaks of the Rocky Mountains? Defend your answer

At sea level because your distance to the center of the Earth is least at sea level.

A very massive object A and a less massive object B move toward each other under the influence of gravity. Which force, if either, is greater?

both forces on each other are the same

When a satellite travels at constant speed, its shape is a(n

circle

An object is placed exactly halfway between the Earth and the Moon. The object will fall toward the

earth

Two objects move toward each other due to gravity. As the objects get closer and closer, the acceleration of each

increases

When the distance between a pair of stars decreases by half, the force between them

increases four times as much

newton discovered

that gravity is universal

A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 s later?

100 m

A projectile is launched vertically at 100 m/s . If air resistance can be neglected, at what speed does it return to its initial level? ASK

100 m/s

Escape speed from Earth is

11.2 km/s.

Ignoring air resistance, what maximum speed can be given to a horizontally moving tennis ball as it clears the net 1.25 m high to remain within the edge of the court, which is 12.0 m from the bottom of the net? ASK

24.0 m/s

Two projectiles are fired at equal speeds but different angles. One is fired at an angle of 30° and the other at 60°. With no air resistance, the projectile to hit the ground first will be the one fired at

30°

With no air resistance, a projectile fired at 60° has the same range as if it were fired at ASK

30°

A ball is thrown horizontally from the top of a tall cliff. Three seconds later, the ball has fallen a vertical distance of ASK

45 m

For each 8-km segment of a satellite in close Earth orbit, the "drop" toward Earth is about

5m

What is the magnitude of the gravitational force between Earth and a 1 −kg body at its surface?

9.8 N

A space vehicle can outrun Earth's gravity, but can it get entirely beyond Earth's gravity?

No, Earth's gravity extends to infinity, decreasing as the inverse square of the distance

A dropped ball gains speed because

a gravitational force acts on it

Consider a space pod somewhere between Earth and the Moon, at just the right distance so that the gravitational attractions to Earth and the Moon are equal. Is this location nearer Earth or the Moon?

nearer the Moon

After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is

the same as it was at the top of its path.

Earth is gravitationally pulled toward

the sun, Jupiter, mars

Nellie tosses a ball upward at an angle. Assuming no air resistance, which component of velocity changes with time?

the vertical component

Consider two planets in space that gravitationally attract each other. If the mass of one planet is doubled, and the distance between them doesn't change, then the force between them is

twice as much

If your mass doubles, your weight

also doubles

Compared to other fundamental forces, the Universal Gravitational Constant G indicates gravity to be a relatively

weak force

Inside a freely-falling elevator you would have no

weight

Inside a freely-falling elevator your

weight is zero

How far must one travel to completely be beyond Earth's gravity?

you cant travel far enough

Your weight is defined to be the force

you exert against a supporting surface.

The hang time of an athlete who moves horizontally 2.0 m during a 1.25-m-high jump is ASK

about 1 s

Without air resistance, a projectile fired horizontally at 8 km/s from a mountain top will

accelerate downward at g as it moves horizontally. return to its starting position and repeat its falling behavior. trace a curve that matches Earth's curvature.

The Moon falls toward Earth in the sense that it falls

beneath the straight-line path it would take without gravity

Acceleration is greatest for a satellite in elliptical orbit when it is

closest to earth

When the distance between a pair of stars doubles, the force between them

decreases to one-quarter as much

Newton did not discover gravity, for early humans discovered that whenever they fell. What Newton did discover is that gravity

extends throughout the universe

Your weight is equal to mg when you are

firmly supported on a horizontal surface and in equilibrium.

The Sun is spherical due to

gravitation.

Compared with the period of satellites in orbit close to Earth, the period of satellites in orbit far from Earth is

greater

t what part of an elliptical orbit does an Earth satellite have the greatest speed? The least speed?

greatest, when closest; least, when furthest

If the Sun were twice as massive

its pull on earth would double, earths pull on the sun would double

Why doesn't the Moon fall toward Earth like apples do?

moon does fall but due to its tangential motion it also falls around Earth

A lunar month is about 28 days. If the Moon were farther from Earth than it is now, the lunar month would be

more than 28 days

When a projectile achieves escape speed from Earth, it

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

The period of a satellite, the time it takes for a complete revolution, depends on the satellite's

radial distance

A projectile that is fired vertically at 5 km/s from the Earth's surface will

rise and fall back to Earth's surface.

A projectile that is fired vertically at 8 km/s from Earth's surface will

rise and fall back to Earth's surface.

This chapter states a link between Newton's Universal Law of Gravity and

the U.S. Constitution.

Occupants of the International Space Station experience weightlessness due to

the absence of a support force.