1. Forces

2. Forces Force: A push or a pull on an object.
A force can effect an object by:
Causing a resting object to move
Accelerating a moving object by changing its speed or direction

3. Forces Force is measured in Newtons, abbreviated as N.
A Newton is the force that causes a 1-kilgram mass to accelerate at a rate of 1 meter per second each second.
(1 kg*m/s2)

4. Types of Forces Contact Forces Friction Force Tension Force
Normal Force
Air Resistance Force
Applied Force
Spring Force
Action at a distance forces
Gravitational Force
Electrical Force
Magnetic Force
Nuclear Force

5. Forces are vectors!
We can add vectors that are the same direction, subtract vectors that are in opposite directions!
Net force is the is the vector sum of all the forces that act upon an object; or the overall force.

6. Free Body Diagrams
You can use arrows to represent the direction and size of a force.
The direction of the arrow indicates the direction of the force.
The length of the arrow represent the size, or magnitude, of the force.

7. Balanced vs. Unbalanced Forces
When the forces on an object are balanced, there is no change in the objects motion
Force of the foot on the wall is balanced with the
force of the wall on the foot = no change in the walls motion.

8. Balanced vs. Unbalanced Forces
When an unbalanced force acts on an object, the object accelerates.
Force of the foot on the ball is greater than the
force of the ball on the foot = unbalanced force. The ball accelerates!

9. Balanced vs. Unbalanced Forces
20 N to the left
20 N to the right
What is the net force acting on the truck?
20 N – 20 N = 0 N
Forces are BALANCED!

10. Balanced vs. Unbalanced Forces
What is the net force acting on the truck?
100 N – 60 N = 40 N to the right
Forces are UNBALANCED!
Truck accelerates in the direction of the greater force.

11. Balanced vs. Unbalanced Forces
What is the net force acting on the truck?
10 N + 10 N – 7 N = 13 N to the right
Forces are UNBALANCED!
The car accelerates in the direction of the greater force.

12. Sometimes you cannot simply add or subtract vectors…

13. Physics of Skydiving

14. Terminal Velocity
Terminal velocity- of a falling body occurs during free fall when a falling body experiences zero acceleration (constant velocity) because the forces of air resistance and gravity are balanced!

15. Can an object still be moving if forces are balanced (zero acceleration)? Explain!