The English physicist Isaac Newton (1642 - 1727) was one of the greatest physicists of all time. His conception of the universe, which he formulated at age 24, lasted for almost
years until the end of the
19 th century when other scientists began finding holes in his theories.

Also called the
An object in motion (or at rest) tends to stay in motion (or at rest) unless acted upon by an external force.

Translation of Newton’s First Law for the
Hood
“
Yo!
My main man. It’s hard to get up in the morning … You-knowwhat-I’m-saying … but once you get up and all , you got the juice and its like … its like easy to keep going … Word ?
Likewise, if you are in your ride without a seatbelt and you know … you slam into a wall … you are just going to be like slamming all up into that wall … and you
WILL keep on going. You feel me?
Driver without seat belt just keeps on moving

CRASH TEST VIDEOS

The following is what would happen to you if you didn’t wear your seat belt and crashed into a solid tree at 90 km/hr.
0 sec –
The front bumper of the car makes initial contact with the tree. The rest of the car, including the driver, is still moving at 90 km/hr

0.01 sec-
The front bumper and grill have collapsed.
Slivers of the material making up the bumper have penetrated the trunk of the tree to a depth of 3 to 4 cm .

0.02 sec-
The grill desintegrates completely. The hood of the car crumples and rises as it smashes into the windshield. The rear wheels, still spinning , leave the ground. The front fenders crumple and rear car body begins to come forward past the front doors of the car. The driver continues to move forward with the car’s initial speed and his legs, which are ramrod straight, snap at the knee joints. The force exerted by the tree has stopped the front of the car and is now affecting the rest of the car with the rate of deceleration or “negative acceleration” declining as one goes to the rear of the car.

0.03 sec–
The driver’s body rises off the seat.
His head nears the sunvisor and his chest moves towards the steering wheel. His broken knees press into the dashboard.
His grip on the steering wheel causes it to bend and the steering assembly begins to collapse.

0.04 sec-
The front 60 cm of the car is now completely demolished. The rear end of the car, however, is still travelling at an estimated 55 km/hr . The engine slams into the tree trunk, causing the rear of the car to rise high in the air. The driver, however, is still travelling close to his original speed of 90 km/hr.

0.05 sec-
The driver’s chest strikes the steering column and the dashboard at a speed nearly 90 km/hr.
The impact collapses his chest, driving his ribs into his lungs and the surrounding arteries. His chest cavity begins to fill with blood.

0.06 sec-
The negative acceleration exprienced by the driver is so great that his shoes are ripped off even though they are tightly laced. But his forward motion continues until his head smashes into the windshield. The rear end of the car and the wheels, still spinning, dig into the ground and the car’s forward motion nears zero .

0.07 sec-
The entire body of the car is now smashed out of shape. Hinges tear and doors spring open. The seat rams forward applying an additonal force on the driver. Shock has probably stopped his heart, and he will die in less than 1.0 sec.

The acceleration of an object is directly proportional to the force applied to it… a

F
…and inversely proportional to its mass. a 

The hanging weight applies a force
(F) to the mass
cart (m) making it accelerate (a) according to F = ma

Suppose we double
the weight of the hanging metal.
What happens to the acceleration of the cart?
F orig
= m
• a orig
F new
= 2F orig m
• a new m
= 2 m
• a orig m a new
= 2a orig

Suppose we double
the mass of the mass cart.
What happens to the acceleration of the cart?
F orig
= m•a
F orig
= a m
F orig
2m
= a new m•a
2m
= a new a
=
2 a new m•a
2m
= a new

Why don’t skydivers continue to accelerate when they jump out of planes? Why do they reach a terminal velocity

For every action there is an equal and opposite reaction.

Force of Gun on Bullet vs.
Recoil of Bullet on Gun
Force of Fist on Face vs.
Force of Face on Fist
Force of Runner on Girl vs.
Force of Girl on Runner
Force of Balloon on Face vs.
Force of Face on Balloon
Force of Man on Pants vs.
Force of Pants on Man

• The two forces shown form an action/reaction pair
• Pay attention to the prepositions
• Gloves protect the other boxer’s face but also the gloved boxer’s hand.

F
2
= force of football player to w:
F
1
F
2
= F
1
= force of football player the right to the left on on football player to the left football player to the right
F
2
F
1
If F
1
= F
2
, how come the results are not the same on both players?
In simplest terms, it is because the player on the left has more mass than
F
= F
1
M
•a = m • a the player on the right and so the player on the right must undergo a greater acceleration than the player on the left.

The boxer’s head has a small mass, therefore, it undergoes a big acceleration
The boxer’s arm and shoulder has a big mass, therefore it undergoes a small deceleration

Canoe pushes on boy’s feet with a Force –F
1
This causes the boy to move forwards.
Boy pushes on canoe bottom with Force F
1
This causes the boat to move backwards.

Constant of Universal
Gravitation
Force of attraction
F g
= G m
1 m
2 r 2
Masses of two objects being attracted to each other
Square of the distance between the objects

Newton’s Cannon
Why don’t satellites fall to the earth if they are being pulled to it by gravity?
• If the cannon shoots a cannon ball at a speed of say 8 m/s , the following will happen…
It falls to earth pulled by gravity

Newton’s Cannon
Why don’t satellites fall to the earth if they are being pulled to it by gravity?
• If the cannon shoots a cannon ball at say
80 m/s , the following will happen…

Newton’s Cannon
Why don’t satellites fall to the earth if they are being pulled to it by gravity?
• If the cannon shoots a cannon ball at slightly less than
8000 m/s , the following will happen…
The cannon ball will fall at the base of the mountain.

Newton’s Cannon
Why don’t satellites fall to the earth if they are being pulled to it by gravity?
• If the cannon shoots a cannon ball at 8000 m/s , the following will happen…
The cannon ball will orbit in a circular path

Newton’s Cannon
Why don’t satellites fall to the earth if they are being pulled to it by gravity?
• If the cannon shoots a cannon ball at a velocity slightly over
8000 m/s , what will happen?
The cannon ball will orbit in an elliptical path

Ans: the earth is always “falling” towards the sun. The reason it doesn’t crash into the earth is that it is moving fast enough that it always “misses”. The earth also has inertia that keeps it on its path.