astronomy exam 2 (section 8)

an ion rocket engine produces 1 newton of thrust. what acceleration can it give to a space probe with a mass of 1000kg?

0.001 m/s^2 yes. calculate: a = F/m = 1/1000 = 0.001

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

50 newtons. yes. F = ma = (5) x (10) = 50

Galileo's approach to understanding moving objects was to

build things that he could measure.

the Law of Inertia says that if an object is not acted on by any outside FORCE

its acceleration will be zero.

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

keep moving at the same speed

when a bullet is fired from a gun, the bullet keeps moving after it leaves the gun barrel because

no force stops it.

when an arrow is fired from a bow, the arrow keeps moving after it leaves the bow because

no force stops it.

aristotle said that a moving earthly or 'mundane" object with nothing pushing or pulling on it will always

slow down and stop

a book, weighing 10 newtons, sits on a table. which of the following pairs of forces is an action-reaciton pair?

the force that the book exerts on the table and the force that the table exerts on the book.

if the acceleration of an object is zero, its speed

is not changing yes. acceleration is defined to be the rate of change of velocity. if the acceleration is zero, then the rate of change of the velocity is zero.

a unit of mass is the

kilogram.

Galileo's approach to science is best described as based on

active construction of simplified experiments.

The Law of Inertia states that a moving object will

keep moving if no force acts on it. yes. an object will move until some force stops it.

an ion rocket engine produces 5 newtons of thrust. what acceleration can it give to a space probe with a mass of 1000kg?

0.005 m/s^2 yes. a = F/m = 5/1000 = 0.005

a solar sail is a large sheet of light-reflecting plastic spread on a n 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?

0.02 m/s^2 yes. a = F/m = 2/100 = 0.02

what total force will cause an object with a mass of 1kg to gain 10 meters per second every second?

10 newtons. yes. F = ma = (1) x (10)= 10

suppose that you lift an object by exerting a upward force of 12 newtons on it. if gravity exerts a force of 10 newtons downward on the object, what is the total force on the OBJECT?

2 newtons. yes. 12 - 10 = 2

what total force will cause an object with a mass of 1kg to gain 5 meters per second every second?

5 Newtons. yes. F = ma = (1) x (5) = 5

suppose that you try to life an object by exerting an upward force of 5 newtons on it. if the gravity exerts a force of 10 newtons downward on the object, what is the total force on the object?

5 newtons.

who discovered Newton's First Law of Motion?

Galileo.

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

both balls would always hit at exactly the same time.

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

both objects would hit the ground at the same time. yes. Galileo proposed that all objects fall the same way, regardless of weight so long as air friction is small enough to be ignored.

a unit of force is the

newton.

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.

aritstotle said that the amount of force on a moving earthly object determines its

speed

the force that acts on a rocket because its engine is firing is exerted by

the exhaust from the rocket.

according to Galileo, a thrown spear keeps moving after it has left the spear thrower's hand because

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

according to aristotle, a thrown spear keeps moving after it has left the spear thrower's hand because

the force of the air disturbed by the spear keeps it in motions

a horse is pulling a cart along a road. which of the following pairs of forces is an action-reaction pair?

the force of the 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 unafffected by air resistance. if one object is twice as heavy as the other, aristotle would predict that

the heavier object would hit the ground long before the lighter one.

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, ARISTOTLE predicted that

the heavier object would hit the ground long before the lighter one. yes. Aristotle figured that more force means more speed, so the heavier object would fall faster.

suppose that you drop a wooden ball and and an iron ball, both the exact same diameter, from the same height at the same time. Aristotle would predict that

the iron ball would hit the ground long before the wooden ball

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

will always be zero. yes. that means the velocity is not changing, which means that the speed and direction are not changing.

if an object is moving at constant speed in a straight line, its acceleration is

zero.