# Newton's Laws Project

#### Lunthar

1. Homework Statement

I have to prove Newton's laws with a practical project, for my school's science competition. This is what I have until now:

3rd law ==> a) Two balls tied with a thread with a spring between them.
b) A rocket/balloon... but I don't know how... any ideas??

1st law ==> a) Fill a recipent with water, put any floating object into it, if there's no force, there won't be any movement.

2nd law==> b) no idea...

Can you help please?? (And excuse my english, greetings from Spain!!)

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#### Lunthar

Thanks, and happy new year 2007! But what I was requesting were practical examples, I understand the laws... but I don't know good ways for proving it... specially for an event like that...

#### andrevdh

Homework Helper
Third law - use Archimede's principle:

Hang an object from a spring scale into a beaker of water resting on an electronic scale.

#### Lunthar

Thanks!! Any idea for second law?

#### andrevdh

Homework Helper
For the first you could slide a (dry?) ice puck over a level glass pane.

The second requires much more effort:
1. Show that the acceleration of an object (constant mass) is directly proportional to the applied force.

2. Show that the acceleration of an object (variable mass and constant applied force) is inversely proportional to the mass of the object.

This then proves that $$a \propto \frac{F}{m}$$

#### Lunthar

Thanks, so I have now an static and in movement practise for first law. But I still don't know how to prove the second one...

#### andrevdh

Homework Helper
... The second requires much more effort:
1. Show that the acceleration of an object (constant mass) is directly proportional to the applied force.

2. Show that the acceleration of an object (variable mass and constant applied force) is inversely proportional to the mass of the object.

This then proves that $$a \propto \frac{F}{m}$$
This part of my previous post refers to "proving" the second law.

#### hover

You could use the acceleration of gravity on a mass on earth to show newtons second law. Newtons second law is F=ma. So you could say that an object at reast on earth is moving 9.8m/s^2. The mass could weigh 1 kilogram so 1 kilogram *9.8m/s^2 will of course equal 9.8 newtons or 2.2 pounds.

#### Lunthar

Good idea! Thank you!