Force and MotionDecember 2014 Benchmark Review

Formula TriangleF=ma

F=ma m=F/a a=F/m

Use your finger to cover the value you are looking for. If the values you already have are next to each other, you multiply. If they are above and below each other, you divide.

Calculate the Mass for the object below(yes, I know it says acceleration on the paper)

Force (N)

Acceleration (m/s2)

5 2.5

10 5

20 10

30 15 Mass = Force/Acceleration

Force (N)

Acceleration (m/s2)

Mass(Kg)

5 2.5 2

10 5 2

20 10 2

30 15 2

Formula TriangleS=d/t

Use your finger to cover the value you are looking for. If the values you already have are next to each other, you multiply. If they are above and below each other, you divide.

Calculating Speed

 

Speed= 200,000 km/s

time=2 sec

distance= 400,000 km

200,000 km/s

2s

Speed Graph

9:30 to 10:00

Distance = 0 (object did not move)

Time = 0.5 hr

S=d/t

S= 0km/.5hr = 0 km/hr

Speed Graph

10:00 to 11:00

Distance = 100km – 60km = 40 km

Time = 1 hr

S=d/t

S= 40km/1hr = 40 km/hr

Speed Graph

10:00 to 12:00

Distance = 60km – 20km = 40 km

Time = 2 hr

S=d/t

S= 40km/2hr = 20 km/hr

Speed Graph

The object moves at a steady rate from 8:45 to 9:30. The object is then at rest for 30 minutes, then continues at a slower steady rate for 1 hour. The object stops briefly, then returns to the starting point at a faster steady rate.

Net Force Diagram

Draw a diagram which shows an object being pushed to the right with a force of 6 newtons and to the left with a force of 3 newtons. Which way will the object move? Will the object’s speed increase, decrease, or remain constant?

6N 3N

The object will accelerate (move with increasing speed) to the right because the greater force is pushing to the right.

How does the force of an object affect the object’s speed?

The more force that is applied to an object, the fast it will go.(Newton’s 2nd Law)

Distance / Time GraphType of Line Increase or Decrease

or Constant

    Constant Speed   

 No Change in Motion

  

 Constant Speed

Velocity / Time Graph

Type of Line Increase or Decrease or Constant

    Increase Speed

     Constant Speed

  

 Decrease Speed

Balanced Forces

Net Force = 0 

If forces are BALANCED then there is no change in motion.

 

Unbalanced Forces

Net Force= >0 

If forces are UNBALANCED, then there is a change in motion.

 

The object will accelerate in the DIRECTION of the

GREATER force.

 

Net Force = 3N to the right

Newton’s 1st Law

Law of Inertia

An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force.

When a car stops suddenly, your body wants to continue to move forward until an outside force (hopefully a seat belt) stops it

Newton’s 2nd Law

F=ma

The acceleration of an object is dependent upon two variables – the net force acting upon the object and the mass of the object.

A rock with a larger mass will require more force to move.

Newton’s 3rd Law

Action / Reaction

For every action there is an equal and opposite reaction

A rockets thrust goes downward to push the rocket upward