What is a Force? Station 2

When you drop something it is pulled to the ground by gravity.

When you ride your bike, your foot pushes against the pedal When you ride your bike, your foot pushes against the pedal. The push makes the wheels of the bike move.

1. What is a Force? Any push or pull which causes something to move or change its speed or direction

2. Give an example of a pushing force and a pulling force at school: ___________________________________________________________________________________________________________________________________________________________________________________________________

3. Forces can affect motion in several ways

They can make objects: Start moving Stop moving Slow down Speed up Change direction Change shape Task: Match up the examples from the station card with the changes in motion they represent. Record your answers in your student packet!

4. Force Facts Forces are measured in Newtons (N) Forces usually act in pairs Forces can usually not be seen but their effects can!

5. How Do Forces Combine? When all of the forces acting on the object are added together, you determine the net force.

Solve the following net force practice problems in your student packet Solve the following net force practice problems in your student packet. Make sure you show your work!!

6. Net Force Practice Problems: Problem A: You and your brother are pushing a car with a dead battery with forces of 20 N and 25 N in the same direction. What is the net force applied on the car?

6. Net Force Practice Problems: Solution A:  Since you are pushing the car in the same direction, the forces will be added together. Net force = 20 N + 25 N Net force  = 45 N

6. Net Force Practice Problems: Problem B: What is the net force on the airplane?

6. Net Force Practice Problems: Solution B:  The airplane is moving with a force of 800 N. However, there are two forces moving in opposite directions on the airplane.  

6. Net Force Practice Problems: Solution B: Just add these two forces: 40 N  + 60 N = 100 N Subtract to get the net force: 800 N  - 100 N = 700 N The net force is 700 N. The airplane will move with a force of 700 N as a result of air friction and wind.  

6. Net Force Practice Problems: Problem C: A brother is pulling a toy from his sister with a force of 6 N. The sister is pulling back with a force of 8 N.  Draw a picture showing the situation and determine the net force. Who gets the toy?

6. Net Force Practice Problems: Problem D: 4 people are playing tug of war. Two are pulling on the right side. Two are pulling on the left side.  On the right side, one is pulling with a force of 60 N and the other with a force of 70 N. On the left side, one is pulling with a force of 30 N.  Draw a picture to represent the situation.

6. Net Force Practice Problems: Problem D: How much force should the second person on the left apply to keep the rope in equilibrium?

7. Balanced Forces All forces acting on an object are equal in size and in opposite directions There is no motion Net force of zero

8. Unbalanced Forces All forces acting on an object are NOT equal in size There IS motion One of the forces is stronger than the other

9. Balanced or Unbalanced? Car at a stop sign

9. Balanced or Unbalanced? Running to first base

9. Balanced or Unbalanced? Books on the desk !

9. Balanced or Unbalanced? Airplane taking off

10. Look at this picture and give two examples of a balanced force and two examples of an unbalanced force: