2. A force is a push or a pull
Simple statement:
A force is a push or a pull

3. Forces add like vectors
Forces are vectors
Forces add like vectors

4. The figure below shows two forces, F1 and F2, acting on an object.
Which force vector best represents the resultant force on the object?
A B C D
E None of the above F1 F2

5. The figure below shows two forces, F1 and F2, acting on an object.
A third force is applied on the object so that the net force on the object is zero. Which force vector best represents the third force?
A B C D
E None of the above F1 F2

6. Newton’s First Law of Motion:
The velocity of an object will not change unless a net external force acts on it.
“Inertia”

7. Newton’s First Law of Motion:
The velocity of an object will not change unless a net external force acts on it.
“Inertia”
Cart Demo

8. Newton’s Second Law of Motion:

9. Newton’s Second Law of Motion:
Units:
“Newton (N)”
named after you-know-who

10. Example:
A book with mass 2.35 kg slides across a table with an initial velocity of m/s. It comes to a stop after sliding 1.75 m. (Assume constant acceleration.)
a) What was the acceleration of the book?

11. Example:
A book with mass 2.35 kg slides across a table with an initial velocity of m/s. It comes to a stop after sliding 1.75 m. (Assume constant acceleration.)
a) What was the acceleration of the book?
b) What force did friction exert on the book?

12. Example:
A rocket car has an engine that exerts a 47,500 N force on it. Starting from rest, the car gets up to 435 m/s in 32.7 s. What is the mass of the rocket car?

13. Newton’s Third Law of Motion
When object 1 exerts a force on object 2, object 2 exerts the SAME force on object 1, but in the opposite direction
This law is sometimes referred to as
“Action – Reaction”
These forces have the same magnitude, but point in opposite directions.
These two forces act on DIFFERENT bodies.
This is ALWAYS true.

14. The Earth exerts a gravitational force of 1. 70 N on an apple
The Earth exerts a gravitational force of 1.70 N on an apple. What gravitational force does the apple exert on the Earth?
A) 0.0 N
B) Something less than 1.7 N
C) 1.7 N
D) Something more than 1.7 N

15. After your car breaks down, you push it to your favorite repair shop
After your car breaks down, you push it to your favorite repair shop. (You know, the one where they know you by name.)
While pushing it at constant speed, how does the force you exert on the car compare to the force the car exerts on you?
A) You exert a greater force.
B) The car exerts a greater force.
C) The forces are the same.

16. After your car breaks down, you push it to your favorite repair shop
After your car breaks down, you push it to your favorite repair shop. (You know, the one where they know you by name.)
While the car is just starting to move, how does the force you exert on the car compare to the force the car exerts on you?
A) You exert a greater force.
B) The car exerts a greater force.
C) The forces are the same.

17. The Space Shuttle accelerated very quickly when it lifted off
The Space Shuttle accelerated very quickly when it lifted off. How did the force the shuttle engines exerted on the exhaust gases compare to the force the exhaust gases exerted on the shuttle?
A) The shuttle exerted a greater force. B) The gases exerted a greater force.
C) The forces were the same.