1. Newton’s Laws of Motion

2. Inertia and Mass
Ancient Greeks observed that objects have natural resting places and objects move toward those places:
A rock falls to the ground
A ball rolls to the bottom of a hill
Once an object is in its natural resting place, it cannot move by itself. A force must act on it to get it to move.

3. Inertia Galileo Galilei – 1600’s Italian Astronomer
Questioned the idea that a force is needed to keep an object moving.
Suggested that once an object is in motion, no push or pull is needed to keep it moving.
Moving or at rest, all objects resist any change to its motion = Inertia.

4. Sir Isaac Newton Discovered the three basic laws of motion.
1st Law of Motion – an object at rest will remain at rest, and an object in motion will remain in motion, unless acted upon by an unbalanced force.
2nd Law of Motion – The net force of an object is equal to the products of its acceleration and its mass. (F = m X a)
3rd Law of Motion – For every action there is an equal and opposite reaction.

5. 1st Law of Motion
1st Law of Motion – an object at rest will remain at rest, and an object in motion will remain in motion, unless acted upon by an unbalanced force. - Law of inertia
The amount of inertia an object has depends on its mass.
The greater the mass, the greater the inertia.
Mass = the amount of matter that makes up an object.
Mass can also be defined as a measure of the inertia of an object.

6. Newton’s 1st Law of Motion
Who has greater inertia?
Who would require more force to move them?
Is this a balanced or unbalanced force?
Sumo has more inertia
because he has greater mass.
Sumo
Unbalanced

7. 2nd Law of Motion 2nd Law of Motion – The net force of an
object is equal to the products of its
acceleration and its mass.
Measured in Newtons (N) = kg•m/s/s
Force = Mass X Acceleration

8. 2nd Law of Motion How do force and mass affect acceleration?
To increase acceleration you could increase the force.
What is the force needed to pull a 52kg water-skier at 2 m/s/s?
What force would be needed to pull a 52kg water-skier at 4 m/s/s?
F = 52 X 2
F = m X a
F = 104 N
F = 52 X 4
F = m X a
F = 208 N

9. 2nd Law of Motion To increase acceleration you could decrease
the mass.
What would a water-skier’s mass be if a force of 104 N was needed to pull them at 2 m/s/s?
What would a water-skier’s mass be if a force of 104N was needed to pull them at 4 m/s/s?
M = F/a
M = 52 kg
M = 104/2
M = F/a
M = 26 kg
M = 104/4

10. Increase Acceleration
Large force + Small Mass =
Increase Acceleration
Small force + Small Mass =
Small Acceleration
Large force + Large Mass =
Small Acceleration
Small force + Large Mass =
Small Acceleration

11. 3rd Law of Motion 3rd Law of Motion – For every action there is
an equal and opposite reaction.
Figure A and Figure B push against
each other with a force of 15N.
Each person will move in an
opposite direction of each
other with equal forces of 15N.

12. Friction & Gravity Forces working against the Laws of Motion:
Friction – the force that one surface exerts on another when the two rub against each other.
Acts in the direction opposite of motion.
Without friction an object would continue to move at constant speed forever.
The strength of friction depends on:
The type of surface involved
Rough = greater friction
Smooth = less friction
How hard the surfaces push against each other
Types of Friction:
Sliding Friction – when two objects slide over one another
Rolling Friction – when an object rolls over a surface
Fluid Friction – when an objects moves through a fluid

13. Friction & Gravity
Gravity – the force that pulls objects toward each other.
Gravity pulls all objects towards the surface of earth at an acceleration of 9.8m/s2
All objects accelerate at the same rate of speed regardless of their mass.
Time
(sec)
Velocity
(m/s) 1
9.8 2
19.6 3
29.4

14. Friction & Gravity
If you drop an elephant and a feather from the top of a building, without any air resistance, which object will hit the ground first?
Hit at the same time due to gravity
pulling on both objects at 9.8m/s2

15. Air Resistance on Gravity
Air resistance – the fluid friction caused by air as an object falls.
Despite the fact that all objects are supposed to fall at the same rate, we know this to not always be true.
Which object would have the greatest effect of air resistance acting against it?
Feather
Bowling Ball

16. Mass Vs. Weight Mass = the amount of matter that makes up an object.
Weight = The force of gravity working on mass.
Weight (N) = mass (kg) X acceleration (m/s2)

17. If Kate has a mass of 25 kg, what would be her weight on:
Earth (gravity = 9.8 m/s/s)
Formula:
Work:
Answer:
The Moon (gravity = 1.7 m/s/s)
W = m X g
= 25 X 9.8
245 N
W = m X g
= 25 X 1.7
42.5 N

18. Mass vs. Weight
Your mass always remains the same ONLY your weight changes due to differences in gravitational forces.