1. Newton’s First Law of Motion*

2. Newton’s First Law
An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force.

3. What does this mean?
Basically, an object will “keep doing what it was doing” unless acted on by an unbalanced force.
If the object was sitting still, it will remain stationary. If it was moving at a constant velocity, it will keep moving.
It takes force to change the motion of an object.

5. What is meant by unbalanced force?
If the forces on an object are equal and opposite, they are said to be balanced, and the object experiences no change in motion. If they are not equal and opposite, then the forces are unbalanced and the motion of the object changes.

6. 1st Law
Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

7. FORCES Forces in Combination
Predict how the box will move based on the forces applied to it.
50N
250N
200N

8. FORCES Forces in Combination
Predict how each box will move based on the forces applied to it.
50N
40N
40N
30N
40N
50N
40N
40N
50N
50N

9. Determine the net force in each example.
FORCES
Forces in Combination
Determine the net force in each example.
23N to the right
29N to the left
30N to the right
15N to the left

10. Check Yourself ? *
Physics 1 (Garcia) SJSU

11. It’s a force we sometimes cannot see – friction.
Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force?
It’s a force we sometimes cannot see – friction.

12. Newton’s First Law is also called the Law of Inertia
Inertia: the tendency of an object to resist changes in its state of motion
The First Law states that all objects have inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).

13. In outer space, away from gravity and any sources of friction, a rocket ship launched with a certain speed and direction would keep going in that same direction and at that same speed forever.
Voyager 1 is a space probe launched by NASA on September 5, The probe has left the solar system 20,638,006,500. KM.
The robotic spacecraft is streaking at 35,000 mph toward an encounter with a star called Proxima Centauri, which lies 17.6 light-years from Earth. It will get there in 40,000 years.

14. Newtons’s 1st Law and You
Don’t let this be you. Wear seat belts.
Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.

15. Newton’s Laws Critical Thinking
A passenger sitting in the rear of a bus claims that she was injured as the driver slammed on the brakes causing a suitcase to come flying toward her from the front of the bus.
If you were the judge in this case, what decision would you make?

16. Demo: Riding Light Rail
When a moving train stops, you continue moving forward.
When the stopped train starts moving again, you remain stationary and are thrown backwards *
Physics 1 (Garcia) SJSU

17. Demo: Rolling, rolling, rolling
All moving together
WALL
Bottom car stops.
Other two continue
With same speed. *
Physics 1 (Garcia) SJSU

18. Demo: Tablecloth Pull Flower Vase Tablecloth Yank quickly *
Physics 1 (Garcia) SJSU

19. Demo: Ring Yank Ring Beaker Coin Yank quickly *
Physics 1 (Garcia) SJSU