Science Study Guide

Question 1

Machines decrease the amount of energy that is needed to do work

Answer 1

True, cause apply less force

Question 2

Because of friction, using machines increase the amount of energy needed to do work

Answer 2

True, cause of friction

Question 3

An arrangement of multiple pulleys cause the direction of the output force to be opposite to the direction of the input force.

Answer 3

True, cause input force is opposite of output force

Question 4

A first class lever can have a input force greater than the output force

Answer 4

When you lift on handle, you don’t need a lot of work

Question 5

If a person tries to lift a heavy box for 5 seconds and can’t make it budge, the work done on the box is less than zero

Answer 5

False, cause it equals zero

Question 6

A second class lever always has an input force that is less than the output force

Answer 6

True, when you lift on the handle you don’t need a lot of force

Question 7

Increasing the angle a ramp makes with the horizontal decreases the mechanical advantage

Answer 7

True, mechanical advantage is equal to length divided by height

Question 8

A meteorologist trying to predict global warming would consider earth to be a closed system.

Answer 8

False, open because there is an exchange of energy and matter

Question 9

A ball falling under the force of gravity is a closed system.

Answer 9

True, no matter is exchanged

Question 10

Increasing the length of a ramp increases the efficiency of the ramp.

Answer 10

True, longer the ramp, less force needed.

Question 11

A quantity that measures the rate at which work is done is called what?

Answer 11

Joules

Question 12

A quantity that measures how much a machine multiplies force or distance is called what?

Answer 12

Work

Question 13

Power is calculated by dividing work by what?

Answer 13

Time

Question 14

Horsepower is the common unit of power in rating engines. However, the official SI unit of power is the what?

Answer 14

Watt

Question 15

All lovers have a rigid arm that turns around a point called the

Answer 15

Fulcrum

Question 16

A —— is defined as a machine made up of more than one simple machine.

Answer 16

Compound machine

Question 17

A —— is an inclined plane wrapped around a cylinder.

Answer 17

Screw

Question 18

The ability to do work defines ——

Answer 18

Energy

Question 19

The formula for calculating kinetic Energy can be written as ——-

Answer 19

KE= 1/2 • m • v 2

Question 20

The stored energy resulting from the relative positions of objects in the system is called ——

Answer 20

Potential energy

Question 21

The energy of a moving object due to its motion is called ——

Answer 21

Kinetic energy

Question 22

The sum of the kinetic energy and potential energy of large-scale objects in a system is called ——-

Answer 22

Mechanical energy

Question 23

Energy that lies at the level of atoms and does not affect motion on a large scale is sometimes called ——

Answer 23

Non-mechanical energy

Question 24

The source of the energy when dynamite explodes is ——-

Answer 24

Chemical energy

Question 25

The process that transforms light energy into chemical energy in plants is called -------

Answer 25

Photosynthesis

Question 26

The source of the energy is -----

Answer 26

Nuclear fusion

Question 27

When a system exchanges energy with the environment outside the system, it is called a -------

Answer 27

Open system

Question 28

A ------- exchanges energy with the outside.

Answer 28

Closed

Question 29

The ratio of useful work output to work input is a measure of -------

Answer 29

Mechanical advantage

Question 30

Energy is transferred as ------- when mechanical energy decreases and temperature increases

Answer 30

Friction

Question 31

Three children exhaust himself trying to push a large rock that doesn't budge. Have they done any work? Why?

Answer 31

No, because the object must move

Question 32

Do machines reduce the amount of work we have to do? If not, why are machines so useful?

Answer 32

No, they only reduce the amount of input force needed to do the job.

Question 33

How does a pendulum show the relationship between gravitational potential energy and kinetic energy?

Answer 33

Because of the gravitational pull on the objects a pendulum swings down then the acceleration brings it up then potential energy brings it back down.

Question 34

What is nuclear fusion?

Answer 34

A kind of reaction in which right atomic nuclear combine to form a heavier nucleus

Question 35

Why is light considered a form of energy?

Answer 35

Because light travels across empty space in the form of electromagnetic waves

Question 36

What is the law of conservation of energy?

Answer 36

Energy cannot be created or destroyed, only transferred.

Question 37

What is the difference between an open system and a closed system?

Answer 37

In the open system matter and energy are exchanged. In the closed system if energy is exchanged, matter is not

Question 38

What is meant by the efficiency of a machine?

Answer 38

The efficiency of the machine is a measure of how much useful work a machine can do. Efficiency equals useful work output divided by work input.

Question 39

Where does energy go when it seems to disappear?

Answer 39

It does not disappear, just changes form