Chapter 5: Models of Motion

An ion rocket engine produces 100 Newtons of thrust. What acceleration can it give to a space probe with a mass of 10,000kg?

0.01 m/s².

What total force will cause an object with a mass of 5kg to gain 10 meters per second every second?

50 Newtons.

An artificial satellite such as the International Space Station stays up because A it falls below a straight-line path in exactly the same way that the curved surface of the Earth does. B Earth's gravity does not extend beyond the atmosphere, so the Space Station is weightless. C its speed weakens the pull of gravity. D it is fixed in the fabric of space. E the shortest distance between two points on the surface of the Earth is a great circle.

A it falls below a straight-line path in exactly the same way that the curved surface of the Earth does.

Aristotle said that the amount of force on a moving earthly object determines its A speed. B acceleration. C time in motion. D distance travelled.

A speed.

If you are told that an object that weighs 20 Newtons is raised a distance of 10 meters, you know that. A the force of gravity on the object is 20 Newtons. B the mass of the object is 20 Newtons. C the force of gravity on the object is 10 meters. D the mass of the object is 10 meters. E the acceleration of the object is 200 kilogram-meters.

A the force of gravity on the object is 20 Newtons.

A solar sail is a large sheet of light-reflecting plastic spread on an extremely low-mass framework and attached to a spacecraft. Sunlight exerts a force on the sail and moves the spacecraft. Suppose the spacecraft has a total mass of 100kg (including the sail) and sunlight exerts a total force of 2N on the sail. What will be the acceleration of the spacecraft? A 50m/s². B 0.02m/s². C 100m/s². D 2m/s². E 0.2m/s².

B 0.02m/s².

Suppose that you lift an object by exerting an upward force of 22 Newtons on it. If gravity exerts a force of 10 Newtons downward on the object, what is the total force on the object? A 22 Newtons. B 12 Newtons. C 10 Newtons. D 2 Newtons. E 120 Newtons.

B 12 Newtons.

The gravitational attraction of the Earth for other objects, A is the same no matter where those objects are. B is smaller for objects farther from the Earth but never vanishes entirely. C extends only as far as the Earth's atmosphere and vanishes for objects like an orbiting space station. D is larger for objects farther from the Earth.

B is smaller for objects farther from the Earth but never vanishes entirely.

A planet that is following Kepler's Laws, accelerates A in the direction of the planets motion. B toward the Sun. C away from the Sun. D between the direction of the planets motion and the direction from the planet to the Sun. E opposite to the direction of the planets motion.

B toward the Sun.

The International Space Station (ISS) is in a roughly circular orbit near the surface of the Earth, moving at around 5 miles per second. Suppose that it is desired to raise it to a new circular orbit, farther from the surface by having a rocket give it one or more short boosts. Which of the following schemes will work? A Increase its speed to 6 miles per second to put it on a rising path. B Increase its speed to 8 miles per second to put it on a rising path. C Increase its speed to 6 miles per second to put it on a rising path and give it another speed boost when its distance from the Earth stops increasing. D Push it directly upward, away from the Earth. E Decrease its speed to 4.9 miles per second and then give it a speed boost when its distance from the Earth stops decreasing.

C Increase its speed to 6 miles per second to put it on a rising path and give it another speed boost when its distance from the Earth stops increasing.

Compare the magnitude of the acceleration of Earth's Moon to the acceleration of falling objects on the surface of the Earth. A the accelerations are the same. B The Moon's acceleration is larger. C The Moon's acceleration is smaller.

C The Moon's acceleration is smaller.

A horse is pulling a cart along a road. Which of the following pairs of forces is an action-reaction pair? A The force of the horse on the cart and the force of the road on the horse. B The force of the horse on the cart and the force of the horse on the road. C The force of horse on the road and the force of the road on the horse. D The force of the cart on the horse and the force of the horse on the road. E The force of the cart on the horse and the force of the road on the horse.

C The force of horse on the road and the force of the road on the horse.

Suppose that you drop two objects from the same height at the same time. Both objects are heavy enough to be unaffected by air resistance. If one object is twice as heavy as the other, Galileo predicted that A the heavier object would hit the ground long before the lighter one. B the lighter object would hit the ground long before the heavier one. C both objects would hit the ground at the same time.

C both objects would hit the ground at the same time.

The recoil or 'kick' of a gun that is firing a bullet is a force exerted on the gun by A the gun itself. B the air around the gun. C the bullet. D the inertia of the gun. E the hand of the shooter.

C the bullet.

According to Galileo, a thrown spear keeps moving after it has left the spear thrower's hand because A the force of the hand keeps acting on the spear. B the force of the air disturbed by the spear keeps it in motion. C the force of friction with the air is not enough to stop the spear. D the force of inertia keeps the spear going.

C the force of friction with the air is not enough to stop the spear.

Suppose that an object with a mass of one kilogram and an object with a mass of two kilograms are both in free fall near the Earth's surface. As compared to the one kilogram object, the two kilogram object accelerates A more because gravity pulls on it more strongly. B less because it has more inertia. C the same because gravity pulls on it more strongly and it has more inertia. D more because gravity pulls on it more strongly and it has less inertia. E less because gravity pulls on it less strongly and it has more inertia.

C the same because gravity pulls on it more strongly and it has more inertia.

If an object is moving at constant speed in a straight line, its acceleration is A positive in its direction of motion. B negative in its direction of motion. C zero. D changing.

C zero.

What total force will cause an object with a mass of 1kg to gain 10 meters per second every second? A 1 Newton. B 9.8 Newtons. C 5 Newtons. D 10 Newtons. E 2.5 Newtons.

D 10 Newtons.

A rocket is in a roughly circular orbit near the surface of the Earth, moving at around 5 miles per second. Suppose that it is desired to lower it to a new circular orbit, slightly closer to the surface. The rocket flips over and fires its main rocket engine in a short burst to slow its speed to 4.96 miles per second. What must it do next?

Slow it's speed again by a bit when its distance from the Earth stops decreasing.

You are standing in an elevator that is accelerating upward at 1m/s². Which of the following pairs of forces is an action-reaction pair that has to be exactly equal and opposite to each other?

The force that the floor of the elevator exerts on you and the force that you exert on the floor of the elevator.

Once its rockets have ceased firing, an Intercontinental Ballistic Missile will follow a path that is best described as

an ellipse with the center of the Earth at one focus.

second law of motion

if a total force F on an object produces an amount of acceleration a, then these quantities are related by the equation F=ma

third law of motion

if object A exerts a force on object B, then object B exerts an equal and opposite force on A. Law of Action-Reaction

If the acceleration of an object is zero, its speed

is not changing

Galileo said that a moving object with nothing pushing or pulling on it will always

keep moving at the same speed.

When Galileo dropped a wooden ball and a heavier iron ball at the same time, he found that

sometimes the wooden ball hit first, sometimes the iron one hit first.

An artificial satellite such as the International Space Station stays up because

the Earth curves out from under it as fast as it falls.

In Newton's Theory of planetary motion,

the Sun and Earth move around each other.

If you are told that a 20 kilogram object is raised by 10 meters, you know that

the mass of the object is 20 kilograms.

One way to change the course of an asteroid is to place a `mass driver' on it. The mass driver is really just a catapult that throws things (like rocks for example) away from the asteroid. The force that acts on the combined object (mass driver plus asteroid) is actually exerted by

the rocks that the catapult throws.

Suppose that an object with a mass of one kilogram and an object with a mass of two kilograms are both in free fall near the Earth's surface. As compared to the one kilogram object, the two kilogram object accelerates

the same because gravity pulls on it twice as strongly and it has twice the inertia.

law of universal gravitation

the scientific law that states that every object in the universe attracts every other object

Newton

understood that it was the acceleration of an object that indicates the force on it. found that, for a planet following an elliptical orbit according to Kepler's Laws, the acceleration always pointed directly toward the Sun and had a magnitude that fell off with distance in proportion to 1/(distance)²

first law of motion

when the total force on an object is zero, its acceleration is also zero.

The Law of Inertia says that if an object is not acted on by any outside force, its acceleration

will always be zero.