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Home / Science projects / Newton’s Laws of Motion
• # Newton’s Laws of Motion

### Inertia: Newton's First Law of Motion

Newton's First Law of Motion, also known as the Law of Inertia, states that an object's velocity will not change unless it is acted on by an outside force. This means that an object at rest will stay at rest until a force causes it to move. Likewise, an object in motion will stay in motion until a force acts on it and causes its velocity to change.

### Newton's Second Law of Motion

Newton's Second Law of Motion states that 'when an object is acted on by an outside force, the strength of the force equals the mass of the object times the resulting acceleration'. In other words, the formula to use in calculating force is force = mass x acceleration. Opposing forces such as friction can be added or subtracted from the total to find the amount of force that was really used in a situation.

You can demonstrate this principle by dropping a rock or marble and a wadded-up piece of paper at the same time. They fall at an equal rate—their acceleration is constant due to the force of gravity acting on them. However, the rock has a much greater force of impact when it hits the ground, because of its greater mass. If you drop the two objects into a dish of sand or flour, you can see how different the force of impact for each object was, based on the crater made in the sand by each one.

Another way to show this is two push off two toy cars or roller skates of equal mass at the same time, giving one of them a harder push than the other. The mass is equal in both, but the acceleration is greater in the one that you exerted greater force on.

• Check out our dynamic carts to gain a better understanding of Newton's Second Law.

### Newton's Third Law of Motion

Stated simply, Newton's Third Law of Motion says that 'for every action, there is an equal and opposite reaction.' Use a pair of roller skates and a ball to show how this works. What happens when you're standing still in skates and then throw a ball hard? The force of throwing the ball pushes your skates (and you) in the other direction.

You can also demonstrate this using Newton's Cradle. This apparatus consists of steel balls suspended on a frame. When the ball on one end is pulled back and then let go, it swings into the other balls. The ball on the opposite end then swings up with an equal force to the first ball, as shown in the illustration on the right. The force of the first ball causes and equal and opposite reaction in the ball at the other end.

For further thought: Thrust is an important result of Newton's Third Law. How does this work in a rocket? Read more about rockets and rocketry.

• Check out our Newton's Cradle for a classic demonstration of Newton's Third Law of Motion.

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By: Dane
Date: Jan 11, 2016

This is great I love physics because you get to know how the things we see almost every day is working

By: Savannah
Date: Nov 04, 2015

So I need to go to the store to buy the material shown above with the balls. Does anyone know what it is called??

[HST adds:  It is called a Newton’s Cradle or Newtonian Demonstrator.  We carry a model on our website here.  http://www.hometrainingtools.com/newton-cradle  Hope this helps!]

By: amitmahla
Date: Sep 15, 2015

according to newton first law of motion

the body is in rest and a body in uniform accelerated motion unless it compelled by external force

and the force acting on the system is greater than the friction of the system then this limit is upper the frcition of the body

than the body moves in accelerated motion

By: Myles
Date: May 13, 2015

Re: Isabelle
Because force = mass x acceleration, if we increase or decrease the mass or rate of acceleration for one variable, the force of the object (the outcome) will change also. Thinking mathematically, if y = (x)(v), and we increase x (aka mass), then the product of (x)(v), which is y, should be greater than the product of another said object with less mass.

In layman’s terms:
(2 kg) X (10 m/s) = (20 N)
However
(10 kg) X (10 m/s) = (100 N)

Likewise for acceleration. Hope I helped :)

By: Isabelle
Date: Mar 24, 2015

How does this demonstrate newton’s second law of motion? It is great though

By: Akok mabior
Date: Mar 12, 2015

Well,the explanation is clear and understandably but it’s much better to show some mathematical representation and example to help the interested student to get a complete information.
thanks

By: Zanaasha
Date: Mar 01, 2015

Helped a lot with a experiment I’m working on in class

By: kainat sami khan
Date: Feb 09, 2015

This is very helpful for my science research homework
THANKS whoever made this website with the specific information

By: Kyari Shah
Date: Nov 19, 2014

It’s very good website and as I am a child I can get a good explanation for my homeworks..

By: Brittney Carmichael
Date: Oct 14, 2014

i love this website it was so helpful but it would be nice if there were pictures to help show what an example of the law represents.!!!!!!!!