Forces

What is a Force?Force:

A push or a pull.

Gives an object energy causing it to start moving, stop moving & change directions.

How are Forces described?A force is described by its strength and

by the direction in which it acts. The direction and strength of a force can be represented by an

arrow.

A force acting to the left A stronger force acting to the right

The arrow points to the direction of the forceThe length of the arrow tells you the strength of the force.

0The longer the arrow, the greater the force.0The strength of a force is measured in the SI unit called a Newton (N).

How do Forces affect Motion?Often more than

one force acts on an object at the same time.

The combination of all the forces on an object is called the net-force.

Balanced ForcesForces that are in opposite directions and

equal in size.

The forces cancel each other out and there is NO MOTION.

The box would not move because there is a zero net force.

Unbalanced ForcesWhen the total force (net force) on an object is in one

direction.

Two forces, one larger than the other therefore the motion will be in the direction of the larger force.

Unbalanced Forces have MOTION!

The box would move LEFT with a Net force of 5N

Recognizing Balanced and Unbalanced Forces

What is the net force on the car?

Net Force =

Is the force balanced or unbalanced?

Recognizing Balanced and Unbalanced Forces

What is the net force on the car?

Net Force = 3NIs there motion?Yes! 3N

Is the force balanced or unbalanced?

Recognizing Balanced and Unbalanced Forces

Both men are pushing on the refrigerator with a force of 100N.

What is the net force on the refrigerator?

Net Force =

Is the force balanced or unbalanced?

Recognizing Balanced and Unbalanced Forces

Both men are pushing on the refrigerator with a force of 100N.

What is the net force on the refrigerator?

Net Force = 0NIs there motion? NO!

Is the force balanced or unbalanced?

Recognizing Balanced and Unbalanced Forces

Both of the people on the left are pulling with a force of 30N to the left. On the right side of the rope, one person is pulling with 35 N to the right, and the other person is pulling with 20N to the right.

What is the net force on the rope?

Net Force =

Is the force balanced or unbalanced?

Recognizing Balanced and Unbalanced Forces

Both of the people on the left are pulling with a force of 30N to the left. On the right side of the rope, one person is pulling with 35 N to the right, and the other person is pulling with 20N to the right.

What is the net force on the rope?

Net Force = 25N

Is the force balanced or unbalanced?

30N 55N