Final Exam Review

Part 1

Motion (questions 1-3)

The definition of motion is any change in position. This is expressed as distance or displacement.It is used to calculate:

speed (distance/time)velocity (distance/time with direction)acceleration (change in velocity)

Speed (#4)

A car travels 15 kilometers in 45 minutes. What is the average speed

Speed = Distance / Time= 15 km / 45 min= 0.33 km/min

Distance (#5)

An airplane flies at 775 km/hr. If it flies for 2 hours, how far has the plane traveled?

Distance = Speed x Time= (775 km/hr) x (2 hr)= 1550 km

Speed (#6)

A marble rolls on a track for 1 meter in 2.5 seconds. What is its speed?

Speed = Distance / Time= 1 m / 2.5 sec= 0.4 m/s

Graphing (#7)

When time is plotted on the x-axis, and distance is plotted on the y-axis, the slope of the graph represents ___________________.

Distance versus time is Distance/Time = Speed

dist

ance

time

Distance vs Time Graphs (8-9)

• What do the slopes represent?• Calculate the slopes.

Acceleration

Define the term Acceleration: • Acceleration is the change in velocity with

respect to time. • Another way to say it is “how fast the velocity

changes”• The formula for acceleration is this context is:

Velocity vs Time (12-14)• Correct the title & label on the graph

0 2 4 6 8 100

2

4

6

8

10

Velocity vs. Time Example

Time (seconds)

Velo

city

(m/s

)

A

B CD

• What do the slopes represent?• What are the slopes at each point?

Acceleration (#15)

• Calculate the acceleration of a car that accelerates from zero to 60km/hr in 5.8 seconds. Check your units.

• a = (60km/hr - 0 km/hr) / (5.8 sec) • a = 10.3 km/hr/sec

Newton’s Laws (#16)

Newton’s first law is also known as:

“The law of inertia”

what does this mean?An object at rest tends to stay at rest unless acted on by an outside force. An object in motion tends to stay in motion unless acted on by an outside force.

Newton’s Second Law (#17-18)

Newton’s second is the relationship between ______________, _________________ and ________________.

What is the formula that relates these?F = m x am = F/aa = F/m

Force MassAcceleration

Inertia (#19 - 20)

Inertia is related to what physical property?

Mass (and mass only)

Inertia is defined as : the property of matter that resists a

change in motion

Acceleration (#21 & #22)

The equation for acceleration is : a=F/m (from #18)

A tow truck pulls a 1,500 kg car with a net force of 4,500 newtons. What is the resulting acceleration? Show your work with the correct units.

a = F/ma = (4500N) / (1500kg)a = 3 m/s2

Force & Mass (#23 & #24)A 20 kg dog on ice skates is accelerating at 2 m/s2. How much force is pushing the dog?

F = m x aF = (20 kg) x (2 m/s2)F = 40 N

A hawk flies by producing a force of 15 newtons. If the bird is observed to accelerate at 10 m/s2, what is the mass of the bird?

m = F / am = (15 N) / (10 m/s2)m = 1.5 kg

Using Graphs (#25-27)

According to the graph above, what is the acceleration when the net force is 3 N?

What is the acceleration with a force of 4 N?

What is the mass of the object in the graph above?

Relationships of “F” & “a” (#28)

Three shots are fired with forces of 50 N, 100 N and 150 N. Which shot resulted in the greatest acceleration?

a = F/mGiven the same mass for each shotthe one with the highest F, also has the

highest acceleration

Misconceptions about weight (#29)

When a heavy object and a light object are dropped from the same height, does one object hits the ground before the other one?

NO – both accelerate at the same rate.more mass means more force, but dividing it by the mass means acceleration is always the sameWhy do we have this misconception?

More gravity (#30)

What is the acceleration of a freely falling object?

The acceleration due to gravity on earth is:9.8 m/s2

This assumes that there is no air resistance, which does affect some things more than others.

Newton’s Third Law (#31)

Why doesn’t a rocket need air to push against in order to fly in space? Explain this using Newton’s 3rd Law.

Newton’s 3rd law states that for every action there is an equal but opposite reaction.When the rocket pushes out exhaust, the exhaust pushes on the rocket. There is no need for anything to push on.

Newton’s 3rd Law (#32)

Newton’s third law talks about force pairs. What are the forces acting on and which direction are they acting?

Newton’s 3rd Law states that for every action there is an equal but opposite reaction. This means that a “force pair” is 2 forces acting on 2 different objects in 2 opposite directions. The forces are also equal in magnitude (amount).

Momentum (#33-35)Define Momentum:

The product of mass times velocityWhat is the formula for momentum?

P = m x vHow is momentum different from inertia?

Inertia depends on the mass, and all objects have it. Momentum is mass times velocity, and only moving objects have momentum.

Intertia vs Momentum (#36)

Which of the following objects has the most inertia? _____ Which has the most momentum?

A 2,000 kg parked carA 20 kg bicycle moving at 10 mph.

The largest mass has the largest inertiaOnly moving objects have momentum

Momentum Calculations (#37)

What is the momentum of a 0.15 kilogram baseball moving at 35 m/s?

P = m x vP = (0.15 kg) ( 35 m/s)P = 5.25 kg•m/s

Momentum Calculations (#38)

A ball is traveling 3.5 m/s when it strikes your IPC teacher on the head. The mass of the ball is 0.03 kg. What was the momentum of the ball when it hit your teacher’s head?

P = m x vP = (0.03 kg) ( 3.5 m/s)P = 0.105 kg•m/s

Momentum (#39)A boy is standing on a skateboard. Together, they have a combined mass of 50 kilograms. The boy throws a 1 kilogram rock forward at 15 m/s. At what speed will the boy roll backward?Momentum Conservation for 2 objects: P1 = -P2

m1v1 = - m2v2

(50 kg) (v1) = - (1kg)(15 m/s)

v1 = - (1kg)(15 m/s)/(50 kg)

v1 = - 0.3 m/s (in the opposite direction of the rock)

Gravitational Potential Energy (#40-41)

Define gravitational potential energy:• The energy associated with an objects position

above the earth. (it’s height)

What is the formula for Potential Energy?

Ep = m x g x h (g = 9.8 m/s2)

Also, Ep = Fw x h because Fw = mg

Kinetic Energy (#42-43)

Define Kinetic Energy:• One-half the product of the mass times the

velocity squared.• More Commonly: “The Energy of Motion”

What is the formula for kinetic energy?

Kinetic vs. Potential Energy Concepts (#44-46)

If you double your mass, what happens to your kinetic energy?– Look at the equation, (double mass doubles EK)

If you double your speed (or velocity) what happens to your kinetic energy?• Look at the equation , the v2 means 4 times the energy

because 22 = 4

Which of the last two questions is true for potential energy?_________ Which is not? _______ Why?

Look at the equation, E = mgh

Force and Energy (#47)

What are the units for the following:• FORCE:

• ENERGY:

newtons, or N

joules, or J

(kg)(m/s2)

N•m, or (kg)(m2/s2)

Energy Examples (#48)

Chemical Potential energy:

Elastic Potential Energy: Gravitational Potential Energy

food gasoline batteries

Stretched rubber band Bent plasticCompressed spring

Car on a hill Rock on a cliff

Kinetic Energy Calculations (#49)

Calculate the kinetic energy of a car with a mass of 2000 kg and a velocity of 5 m/s:Get the equation :

EK = (0.5) (2000kg)(5m/s)2

EK = 25,000 J

Potential Energy Calculations (#50 & 51)What is the potential energy of the 2000 kg car when it is parked that the top of a hill 20 meters high?

EP = m x g x h

EP = (2000 kg)(9.8 m/s2)(20m)

EP = 392,000 J

What is the Kinetic energy of the car when it rolls down the hill? (think conservation of energy)

No need to calculate Ek(bottom) = Ep (top)

Energy Conversions (#52)

When a fossil fuel is burned, where does the energy end up?• The burning process converts the chemical

potential energy of the fossil fuel into heat (Thermal Energy)

• This Thermal Energy may be converted into other forms as well.

Energy Conversions Continues (#53)

When a moving car stops, its kinetic energy is converted into what form of energy?

The ultimate end for all of this energy is heat (Thermal Energy)

It is caused by friction with the breaks.

Kinetic vs Potential Energy

Which kind of energy is often called “The energy of motion?”

Kinetic Energy

Which is often called the energy of position?

Gravitational Potential Energy

Energy (#55)

The wise use of energy is called:

Conservation

Why is this important?

We are running out of fossil fuels(among other reasons)

Fossil Fuels (#56-57)

• Three Types of Fossil Fuels

–Coal–Natural Gas–Petroleum (oil)Only coal is comes only from plants

Alternative Energy (#58)

Name 4 more sources of alternative energy:SOURCE PRO CONWindno fuel not always blowing

Hydroelectric no fuel limited places

Geothermal earth’s heat limited places

Tidal Power no fuel corrosion

Solar (photovoltaic) sunlight night time

Renewable Energy (#59)

What is the difference between renewable energy sources and non-renewable energy sources?

Renewable energy sources either do not use traditional fuels or use a fuel that can be replaced as quickly as it is used. Examples are biomass or biofuels, hydroelectric (rainwater), etc.,

Alternative Energy (#60)

Why must we study more about alternative forms of energy?

• We will eventually run out of fossil fuels• Some forms of energy cause pollution

Fission (#61, #63 & #64)

Define Fission:

• The splitting of a large atom into smaller ones• This is the kind of energy we use in a nuclear

power plant• The fuel is usually Uranium-235, or U-235

Fusion (#62 & #63)

Define Fusion:

• The joining (fusing) of two small atoms into a larger one (typically hydrogen into helium)

• This is the kind of used by the sun• We can’t currently duplicate it in large enough

quantities to make it useful

Nuclear Reactors (#65)

How is a nuclear reactor controlled?

• Control rods made of boron or cadmium slow down the nuclear reactions in the core

Electricity Generation (#66)

Describe the process of generating electricity:

• Combustion of coal produces heat• The heat turns water into steam in a boiler• The steam from the boiler spins a turbine• The turbine is connected to a generator• The generator spins and makes electricity

Conservation of Energy (#67)

• Define the Law of Conservation of Energy:

• Energy cannot be created or destroyed. It can only be transformed from one form to another.

ELECTRIC CIRCUITS (use Exam 7 review)

Study your electric circuits quiz/review• Electric current is measured in Amps (A) and

has the symbol “I” in an equation• Resistance is measured in Ohms () and has the

symbol “R” in an equation• Voltage is measured in Volts (V) which has the

symbol “V” • Ohm’s Law is the relationship among the things

shown above

• Open Circuit: - has a break/off• Closed Circuit: - complete loop/on• Short Circuit: - path with no resistance

(dangerous)• Circuit Breaker / Fuse: Protects equipment or

wiring from too much current