1.
Measuring Force
Force is measured in Newtons (N)

2. Balanced/Unbalanced Forces
Balanced/Unbalanced Forces
Forces are described in terms of ___________ and ____________ (strength).
direction
magnitude
Ex1: Pushing the box to the right
100 N
Ex2: Downward gravitational force
3 N

3. net force
The ______________ is the combination of all the forces acting on an object.
Gravitational force of 15 N
Ex3:
Lift force of 15 N
Net force: __________
0 N
Ex4:
1,050 N
Net force: __________
650 N
400 N

4. Example 3 & 4 explanation:
Example 3: A waitress carries a tray which has a gravitational force of 15 Newtons downward on the tray and she applies a lift force of 15 Newtons up on the tray. They tray is currently flat and stationary. What is the net force applied to the tray? Answer: 0 Newtons (The forces counter each other because they are applied in opposite directions, so you subtract the forces to get the net force. They cancel each other out. 15 – 15 = 0 Newtons.)
Example 4: Billy and Jane are pushing their car out of mud. They are both pushing from behind the car. Billy is pushing with 650 Newtons of force and Jane is pushing with 400 Newtons of force. What is the net force applied to the car? Answer: 1,050 Newtons toward the car. You add the forces applied together because they are being applied in the same direction – they are both trying to move the car out of mud.

5. Ex5: 125 N 375 N 250 N Net force: __________
Example 5: Tom and Dan are pushing a box on opposite sides to see who is stronger. Tom is pushing at one side of the box with 125 Newtons of force. Dan is pushing the same box from the opposite side with 375 Newtons of force. What is the net force applied to the box? Answer: 250 Newtons towards Tom. Dan is applying more force than Tom and so the box is going to move in Tom’s direction.

6. Balanced forces stays still Ex6: 0 N
____________________ – forces acting on any object that combine and form a net force of zero. -When balanced forces are acting on an object, the object _________________.
Balanced forces
stays still
Ex6:
300 N
300 N
Net force:
__________
0 N

7. Unbalanced forces motion Ex7: 100 N
__________________ - forces acting on an object that combine to a net force that is not zero. -Objects go into ___________ because of unbalanced forces.
Unbalanced forces
motion
Ex7:
400 N
500 N
Net force:
__________
100 N

8. Complete Balanced/Unbalanced WS

9. QOD#26
There is a drag force of 300 N on the plane, and the plane has a thrust force (going forward) of 2,500 N. What is the net force of the plane? (answer in complete sentences)
2,200 N

10. Newton’s 3 Laws of Motion

11. First Law of Motion rest rest unbalanced book sitting on a shelf
rest
rest
An object at _______ will remain at _______ unless acted on by an _______________ force.
Ex: _____________________
A book on a shelf will remain on a shelf unless someone picks it up or knocks it off the shelf.
An object in _______ continues in _______with the same _________ unless acted upon by an _______________ force.
unbalanced
book sitting on a shelf
motion
motion
velocity
(speed & direction)
unbalanced
train moving along a track (unbalanced force is friction)

12. First Law of Motion
Newton’s First Law is often called “____________________” ________ – the tendency of an object to _________ a change in motion. Ex:_______________________
The Law of Inertia
Inertia
resist
A ball rolling down a hill, has a tendency to stay rolling

13. 1st Law…
If you throw a ball in space, the ball will stay in motion the same velocity unless acted upon by another force. For example, if it hits an asteroid, meteoroid, or another planet, that would change the velocity of the ball.
A kicked soccer ball on the grass would maintain the same velocity (speed and direction) if it didn’t have the force of friction to slow it down as it travels on the grass.

14. 1st Law…
Ex: ­­­­­­­­­­While a car accelerates forward, the coffee in a cup remains in the same position; subsequently, the car accelerates out from under the coffee and the coffee spills in your lap. On the other hand, when braking from a state of motion the coffee continues forward with the same speed and in the same direction, ultimately hitting the windshield or the dash. Coffee in motion stays in motion.
Ex: When you are riding in a car and if the car hits a wall and is forced to stop, your body has inertia and has the tendency to stay in the same motion, which is why we wear seat belts.

15. Ben is being chased through the woods by a bull moose that he was attempting to photograph. The enormous mass of the bull moose is extremely intimidating. Yet, if Ben makes a zigzag pattern through the woods, he will be able to use the large mass of the moose to his own advantage. Explain this in terms of inertia and Newton's first law of motion. The large mass of the bull moose means that the bull moose has a large inertia. Thus, Ben can more easily change his own state of motion (make quick changes in direction) while the moose has extreme difficulty changing its state of motion.

16. 1st Law…
Watch these short videos that demonstrate Newton’s 1st Law & inertia.

17. Second Law of Motion mass force accelerate mass acceleration MA
The greater the ______ of an object, the greater the amount of ________ needed to ___________ the object.
Ex:______________________
Force = _______ x ___________
F =
*more detail on this equation later
force
accelerate
Its harder to stop an elephant than a toddler from running (see description on next slide)
mass
acceleration MA

18. Example description:
Ex: Consider the mass of an elephant and a toddler. The mass of the elephant is much greater and therefore needs a much greater force to accelerate (put it into motion from rest) the elephant than it takes to accelerate the toddler. The opposite is also true. If an elephant and a toddler are charging at you, the elephant requires a much greater force to stop than does the toddler.

19. 2nd Law… Watch short video

20. Third Law of Motion
For every action (force) there is an _______ and __________ _________. Ex: ___________________
equal
opposite
reaction
Swimming
(action – pushing water behind you,
reaction – moving forward)

21. 3rd Law…
This law means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs. 

22. 3rd Law…
Ex: Consider the motion of a car on the way to school. A car is equipped with wheels that spin. As the wheels spin, they grip the road and push the road backwards. Since forces result from mutual interactions, the road must also be pushing the wheels forward. The size of the force on the road equals the size of the force on the wheels (or car); the direction of the force on the road (backwards) is opposite the direction of the force on the wheels (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for cars to move along a roadway surface.

23. While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus? Trick Question! Each force is the same size. For every action, there is an equal ... (equal!). The fact that the firefly splatters only means that with its smaller mass, it is less able to withstand the larger acceleration resulting from the interaction.

24. Complete Newton’s Laws WS

25. Newton’s 2nd Law Equation
5-1-14
Newton’s 2nd Law Equation
Newton’s 2nd Law gives us an exact relationship between force, mass, and acceleration.
Units
(a) Acceleration m/s2
(m) Mass kg
(F) Force N
Equations
F = ma
a = 𝐅 𝐦
1 N = 1 kg ∙ m/s2

26. Ex1: What is the acceleration of a 3 kg object, if a force of 12 N is used to move it? F = m = a =
a = 4 m/s2

27. Ex2: Brad’s car weighs 1,000 kg and is out of gas
Ex2: Brad’s car weighs 1,000 kg and is out of gas. Brad pushes the car at an acceleration of 0.5 m/s2. What force did Brad push? F = m = a = ?
1,000 kg
0.5 m/s2
F = ma
F = 1,000 kg ∙ 0.5 m/s2
F = 500 kg ∙ m/s2
F = 500 N

28. Complete Newton’s 2nd Law Equation WS