Energy and SM Review

Energy & Simple Machines Review

What is energy?

• Energy is the ability to do work or cause change

• Energy has many forms.

• Even though energy can change from one form to another, energy cannot be created or destroyed. This is known as the law of conservation of energy

Multiple Choice

What is energy?

• moving energy

• stored energy

• renewable energy

• The ability to do work.

Multiple Choice

Energy can be transformed into many different forms:

• True

• False

Multiple Choice

The Law of Conservation of Energy states:

• Energy can created or destroyed but not transformed 

• Energy cannot be created or destroyed, it can only transformed

• Energy can't be created, destroyed or transformed

Forms of Energy

​Type of Energy	Definition​
​Mechanical energy	​The combination of both potential & kinetic energies working together in a system
​Light energy (radiant)	​Energy due to electromagnetic radiation that is visible to the human eye
​Chemical energy	​A type of potential energy stored in the bonds of molecules in substances like foods & batteries
​Sound energy	​Caused by waves of vibrations through the air
​Electrical energy	​Energy due to the movement of charged electrons
​Thermal energy	​Heat energy coming from particles bumping together
​Gravitational energy	​Type of potential energy stored in an object due to its height above the Earth

Multiple Choice

What is the form of energy that is created using heat? This form of energy makes particles of matter move faster.

• light energy

• thermal energy

• chemical energy

• kinetic energy

Multiple Choice

Mechanical energy

• energy built up before being in motion

• energy released in a chemical reaction

• energy of motion

• sum of kinetic and potential energy

Multiple Choice

what type of energy is stored in a battery?

• electrical

• chemical

• thermal

• mechanical

Multiple Choice

Mr. Huff's students are complaining that it is hot in the classroom. He plugs in a fan and turns it on, what energy transformation now occurs?

• mechanical to electrical

• electrical to mechanical

• chemical to mechanical

• electromagnetic to mechanical

Multiple Choice

Electrical Energy is transferred to _____ Energy.

• Thermal

• Solar

• Electrical

• None

Potential vs Kinetic Energy

​Potential Energy

• Stored energy due to an object's position

• The higher the object, the more potential energy it has

Kinetic Energy

• Energy due to motion

• The more speed and mass an object has the more kinetic energy it has

Multiple Choice

The energy of moving matter

• gravitational potential energy

• elastic potential energy

• kinetic energy

• potential energy

Multiple Choice

Energy that is stored in a person or object.

• potential energy

• energy conversion

• law of conservation of energy

• kinetic energy

Potential vs Kinetic Energy

• Potential energy can transform into kinetic energy

• When potential energy is high, kinetic energy is low

• When potential energy is low, kinetic energy is high

• Total energy remains the same

Multiple Choice

At which point is potential energy greatest?

• W

• X

• Y

• Z

Multiple Choice

At which point is kinetic energy greatest?

• W

• X

• Y

• Z

Multiple Choice

As a pendulum swings from its highest to lowest position, what happens to its kinetic and potential energy? 

• Both the potential energy and kinetic energy decrease

• The potential energy decreases while the kinetic energy increases 

• The kinetic energy decreases while the potential energy increases 

• Bothe the potential energy and kinetic energy increase 

What is Work?

• In physics, work is defined as the use of force to move an object. For work to be done, the force must be applied in the same direction that the object moves.

• Work is directly related to both the force applied to an object and the distance the object moves. It can be represented by the equation: Work = Force × Distance.

Multiple Choice

For work to be done on an object, the direction and force have to be going the same direction.

• True

• False

Multiple Choice

A child pushing his baby brother in a stroller.

• Work

• Not work

Multiple Choice

Pushing on a car but it does not move.

• Work

• Not work

Multiple Choice

Which situation is work not done?

• lifting a 20 pound box off the floor

• holding a 20 pound box above the floor

• sliding a 20 pound box across the floor

• sliding a 20 pound box up an inclined plane

Calculating Work

Work, distance, and force are all related. The work equation can be rearranged to find force or distance if . the other values are known

• Work= Force Distance  SI unit of work- Joule (Nm)

• Force= Work ÷ Distance  SI unit of force- Newton (N)

• distance= Work ÷ Force SI unit of distance- meter (m)

Multiple Choice

What is the formula for work?

• Force = work x distance

• Distance = force x work

• Work = force x distance

• Work = force x mass

Multiple Choice

Fred kicks a ball with a force of 20N to George, who is 5M away. How much work was done to the ball?

• 25J

• 100J

• 4J

• 75J

Multiple Choice

The unit used to measure work is the 

• Watt

• Newton

• Joule

• meter

Multiple Select

Two factors that determine work are

• force

• acceleration

• mass

• distance

• velocity

Multiple Choice

500 J of work is done by a person who uses a force of 50N to move a box, how far does it go?

• 10 m

• 0.1 m

• 25,000 m

• 10 J

Simple Machines

Simple machines make work easier. They have few or no moving parts and they work by changing the direction of a force or the amount of force needed to do something.

There are six simple machines

• inclined plane

• wedge

• screw

• pulley

• lever

• wheel & axle

Multiple Choice

Identify this simple machine

• Lever
• Wheel & Axle
• Inclined Plane
• Screw

Multiple Choice

Name this simple machine.

• Lever

• Wedge

• Pulley

• Inclined Plane

Multiple Choice

What is this simple machine?

• Wedge

• Inclined plane

• Lever

• Screw

Making Work Easier

A machine makes work easier by changing at least one of three factors. A machine may

● change the amount of force you exert

● change the distance over which you exert a force

● change the direction in which you exert a force

​Machines do not make work easier by changing the amount of work. The work that goes into a machine must be the same as the work that comes out according to the law of conservation. Machines make work easier by changing the force or the distance over which the force is applied. If you decrease the force you must increase the distance. If you increase the force, you have to decrease the distance.

Multiple Choice

Which of the following is NOT one of the things a machine can do?

• Changes the amount of force required.

• Changes the distance over which the force is exerted.

• Changes the direction of the force.

• Changes the amount of work done.

Multiple Choice

Simple machines can make work easier by reducing the input force needed to move an object. However, there is a trade off for decreased input. What is the trade off?

• The distance the object is moved is increased.

• The distance the object is moved is decreased.

• The amount of work is increased.

• The amount of work is decreased.

Labeling Simple Machines

Input forces

The work you do on a machine is known as input or effort. There are two input forces- effort force & effort distance

• effort force (input force)- force that you exert on the machine (Fe)

• effort distance (input distance)- distance over which the effort force is exerted (De)

​Output Forces

The work done by the machine on the object is known as the output. There are two output forces- resistance force & resistance distance

• resistance force (output force)- force that opposes the motion (Fr)

• resistance distance (output distance) - distance over which the resistance force is exerted (Dr)

Multiple Choice

What is effort (input) force?

• the force one exerts on a machine

• the force which an effort force must overcome in order to do work on an object via a simple machine.

• the force the machine exerts on a object

• the output work times the input distance

Multiple Choice

What is resistance (output) force?

• the force required by a machine in order to accomplish work (the force you put on the machine)

• The force that is exerted by a machine; force that resists motion

• the force the machine exerts on a object

• the output work times the input distance

Multiple Choice

What is effort (input) distance?

• the force required by a machine in order to accomplish work (the force you put on the machine)

• the force which an effort force must overcome in order to do work on an object via a simple machine.

• the distance an input force acts through

• the output work times the input distance

Multiple Choice

What is resistance (output) distance?

• the force required by a machine in order to accomplish work (the force you put on the machine)

• the force which an effort force must overcome in order to do work on an object via a simple machine.

• the distance an input force moves a machine

• the distance through which the output force is exerted

Ideal vs Actual Mechanical Advantage

Mechanical advantage (MA) is the factor by which a machine multiplies the force put into it. The higher the mechanical advantage, the less input force (effort force) is required.

There are two types of mechanical advantage

1. Actual mechanical advantage considers external factors such as the loss of energy due to friction and heat.

2. Ideal mechanical advantage does not consider external factors. This means that ideal mechanical advantage has a higher efficiency or ratio of output work to input work

Multiple Choice

Which type of mechanical advantage considers the loss of energy due to heat & friction?

• actual mechanical advantage

• ideal mechanical advantage

Multiple Choice

the percentage of the input work that is converted to output work

• mechanical advantage

• efficiency

• joule

• machine

Calculating Mechanical Advantage

The formula for mechanical advantage is effort distance/ resistance distance. This looks different for every machine

Multiple Choice

The IMA (ideal mechanical advantage) formula for simple machines

• output/input

• input/output

• effort distance/ resistance distance

• resistance arm length/effort arm length

Multiple Choice

What is the IMA of this lever

• 90

• 33

• 10

• 28

Multiple Choice

What is the mechanical advantage of this pulley system?

• 2

• 3

• 4

• 5

Multiple Choice

the mechanical advantage of a wheel and axle is...

• wheel diameter / force

• wheel radius / axle radius

• axle diameter / wheel diameter