1. Force and Newton’s 3 Laws of
Motion
Reginald Cruz| Illiana Aguirre| Physics 270

2. What is Force and Newton’s 3
Laws of Motion?
Today, we’re going to explain what Force is, Newton’s 3 Laws, and Gravity with Weight

3. Force and Newton’s 3 Laws of Motion
• Force is anything that pulls or pushes an object. The amount of force to the
object will change the motion of the object or prevent the object from chaning
motion.
• Example: DragonBall Z throws a fireball at Chung-Li (Streetfighter) during a
battle. The amount of force Z uses to throw the fireball can change the
motion of where the fireball will hit, in this case, it will knock Chung-Li down to
the ground on impact.

4. Newton’s Three Laws of Motion
• Law of Inertia-Page 126: “A Body that is in motion continues in motion with
the same velocity (at constant speed and in a straight line) and a body at rest
continues to rest unless an unbalanced outside) force acts upon it”.
• Law of Acceleration-Page 128: “The total force acting on a body is equal to
the mass of the body times its acceleration”.
• Law of Action and Reaction-Page 140: “For every force applied by object A to
object B (action), there is an equal but opposite force exerted by object B to
object A (reaction)”.

5. Law of Inertia
Example
• A car moving on the
road in motion will
continue to move
until it stops.
2nd example
• When riding a bus
(like Muni or BART),
also applies to
Newton’s first law.
The bus stops at a
point in time, then it
will stay at rest until
it moves on.
Third example
• Walking from one
point to another
follows Newton’s first
law.
• If you stop at a
midpoint and rest,
then you will stay at
rest then use more
velocity unless an
unbalanced force
acts upon it.

6. Law of Acceleration (Newton’s 2nd
Law)
It states the total force acting on a
body is equal to the mass of the
body times its acceleration.
The equation is F = ma where F is the total force, m = mass, and a = acceleration
Here’s how we would use it: Back to the first scenario on the battle between Dragonball Z and
Chung-Li. What force is necessary for Chung-Li to throw a fireball back at Dragaonball Z if the
mass (m) of the fireball is 1500 kg and the acceleration of the fireball is 100 m/s2.

7. Solution
• First, we know m = 1500 kg and a = 100 m/s2 and F = ?
• The equation is F = (1500 kg)(100 m/s2)
• The amount of force is 150,000 kg m/s2 or 150,000 N (1 N = 1 kg m/s2)
needed for her shot to hit Dragonball Z.

8. Another example of Newton’s 2nd Law
• What is the acceleration of a ball being kicked by a force of 950 N applied to
the mass of 900 kg?
• The Force = 950 N and Mass = 900 kg and a = ?
• To find the acceleration, F = ma  a = F/m
• Then a = (950 N)/(900 kg)
• which a = (950 N)/(900 kg) * 1 kg m/s2/1 N
• The acceleration of the ball is 1.05 m/s2.

9. Gravity and Weight
• The weight of an object is based on the amount of the gravitational pull
exerted on an object by the earth.
• An example is if a satellite dish falls from space as it enters the earth’s
atmosphere. The weight of the dish is being pulled by the gravity from earth.
• It also gives this equation (Section 5.3 Page 131): Fw = mg where Fw = the
weight, m = mass, g = acceleration due to gravity, g = 9.80 m/s2 or g = 32.2
ft/s2.

10. Problem Scenario involving Gravity and Weight
• What is the weight of a rock with a mass of 350 kg?
• Solution: m = 350 kg g = 9.80 m/s2 Fw = ?
• Fw = (350 kg)(9.80 m/s2) 3430 kg m/s2 or 3430 N (1 N = 1 kg m/s2)

11. Works Cited
Ewen, Dale, Neill Schurter and Erik P Gundersen. Applied Physics . 10th Edition. Upper Saddle River: Peasrson Education Inc,
2012. textbook. 7 April 2015.