35 terms

Force/Motion Key Concepts 8th Grade

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P = MV
P = momentum
What is the formula for momentum?
Mass = Momentum divided Velocity
M = P/V
What is the formula for mass (if you know velocity)?
V = P/M

OR: V = distance/time

Remember P = MV (Momentum = Mass x Velocity)
What is the formula for velocity?
A = F/M
Acceleration = Force/Mass

OR
Acceleration = Velocity/Time

In other words, you are increasing or decreasing velocity over time
What is the formula for acceleration?
F = M x A
Force = Mass x Acceleration
What is the formula for force?
= What is Newton's Second Law?
W = M x G
G is gravity

Note: This is the same formula as
F = M x A
Force = mass x acceleration
Force is weight and gravity is the acceleration.
What is the formula for weight?
Power = work / time
What is the formula for Power? *

force x distance
force / distance
work x time
work / time
force x mass
force / mass
force x time
force / time
Newtons (N)

Note:
Kilograms (kg) = Mass
Meters per second square (m/s^2) = Acceleration
Meters per second (m/s) = Velocity
Which is a unit of Force? *

Kilograms (kg)
Newtons (N)
Meters per second square (m/s^2)
Meters per second (m/s)
Meters per second square (m/s^2)
Which is a unit of acceleration? *

Kilograms (kg)
Newtons (N)
Meters per second square (m/s^2)
Meters per second (m/s)
kilograms x meters per second (kg m/s)

P = M x V
Momentum = Mass x Velocity
Which of the following is a unit of momentum? *

meters per second (m/s)
kilograms (kg)
newtons (N)
kilograms x meters per second (kg m/s)
meters per second square (m/s^2)
meters
Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. = inertia
What is Newton's First Law?
For every action, there is an equal and opposite reaction.
Ex. When you shoot a cannon the cannonball moves forward very fast and the cannon moves backwards.
What is Newton's Third Law?
Newtons
= force that would give a mass of one kilogram an acceleration of one meter per second per second,
What is the measure of weight?
9.8 Newtons
Because the gravity on earth is 9.8 m/s²
What is the weight of 1 KG on earth?
Because the cannon has more mass.

Remember Newton's Third Law. For every action, there is an equal and opposite reaction.

P = M x V (Momentum = Mass x Velocity)
so
V = P/M

The momentum is the same for the cannonball and the cannon but the velocity is more for the cannonball because it has less mass.
Why is the velocity of the cannonball (going forward) much more than the velocity of the cannon (moving backward)?
Fluid Friction
Which type of friction is experienced by an object that is falling through the air.

-Sliding Friction
-Rolling Friction
-Fluid Friction
-No Friction
Terminal Velocity
In a falling object what is the term when the force of friction equals the force of gravity. *

Normal Force
Unbalanced Force
Terminal Velocity
Acceleration
Deceleration
Rolling Friction
In the picture below of the "after" cannon is fired, what type of friction does the cannon experience? *

Sliding Friction
Rolling Friction
Normal Friction
Fluid Friction
No Friction
Joules
Which is the unit of energy? *

Newtons
Watts
Joules
Kilogram meters per second
Newtons per second
Inertia

= Newton's First Law of Motion
The resistance of an object to any change in motion. *

Newton's Second Law of Motion
Inertia
Newton
Joules
Newton's Third Law of Motion
Motion
A change in position with respect to a reference point. *

Force
Work
Energy
Motion
Power
mass
Momentum
Weight
Power
Watts is a unit of: *

Energy
Work
Power
Force
Distance
Momentum
Force = mass x acceleration
Momentum = mass x velocity

A force is required to change the momentum of any object. In a car crash, the car and the person have momentum. If the car hits a wall, the wall exerts a force on the car which stops its momentum. However, the wall does not exert a force on the person, so they keep going and are thrown forward.
What is the difference between force and momentum?
Mass = how much material there is. Doesn't change in different gravity.
How many KG is the car? Ex. 2000 KG
Weight = how much force is there because of gravity.
How many Newtons is the car on earth? = 9.8 (gravity) x 2000KG = 19,600 Newtons
Velocity = How far it moves in a certain time. &
Speed in a particular direction
Formula: Velocity = Distance/Time
Units = Ex. 100 km/hour = 28 meters/second
How fast is the car going?
Distance - change in position
Formula: D = V x T
Ex. 100 meters = 50 m/s x 2 seconds
How far does the car move?
Time
Formula: T = D/V
Ex. 2 seconds = 200m divided by 100m/s
Unit = seconds, minutes, hours
How long does it take to move the car 200m?
Momentum = the velocity of a mass
Formula: P = M x V
Units = KG x meter/second (kg m/s)
Note that the car's momentum is more than the driver's momentum because the car has more mass.
How fast is the 2000kg car moving? How about the driver?
Acceleration = change in velocity
Formula: Force/Mass (Because F = M x A)
Units: Meters per second per second (m/s^2)
Ex. 2m/s^2 = 4000N/2000kg
How fast is the velocity changing? Ex. you hit the brakes and go from 100 KPH to 50 KPH in 3 seconds OR hitting the gas and going from 0 KPH to 100 KPH in 5 seconds.
Force = the thing that changes the acceleration
Formula: F = M x A
Unit: Newtons
Ex. 4000N = 2000kg x 2m/s^2
How much you need to accelerate the 2000kg car? Ex. Change the velocity from 0 m/s to 2 m/s.
Work = the distance you can move a mass in a certain time
Formula: Work = mass x distance (you move it)
Unit = joules
Ex. 10kg x 1000m
How far can you move the 100kg wheelbarrow in 10 seconds?
Power = the rate at which the energy is used over time
Formula: Power = work/time
Unit = Watts
How much do you need to move the 100kg wheelbarrow 100 meters in a 5 seconds?
Energy = what is transferred to get work done
= mass x gravity x height
Ex. 10kg x 9.8Newtons x 10meters = 980 kg m2 / s2
Unit = Joule
What is stored in the rock that has been lifted up by a pulley?
Mass = How many KG is the car? Ex. 2000 KG

Weight = How many Newtons is the car on earth? = 9.8 x 2000 = 19,600 Newtons

Velocity = How fast is it going? Ex. 100 km/hour = 28 meters/second

Momentum = How fast is the mass moving?
The car's momentum is more than the driver's momentum because the car has more mass.

Acceleration = How fast is the velocity changing? Ex. you hit the brakes and go from 100 KPH to 50 KPH in 3 seconds OR hitting the gas and going from 0 KPH to 100 KPH in 5 seconds.

Force = How much you need to accelerate the mass to that speed? OR How much you need to slow down the mass?
Talk about the picture of the car using these words:

Mass
Weight
Velocity
Momentum
Acceleration
Force