## Saturday, November 17, 2012

### Newton's 3 Laws of Motion

~ For the past two weeks, we have been studying Newton's three laws of motion by performing the hover disc lab and the fan cart lab.

Newton's 1st Law
An object at rest or traveling at a constant speed will continue to do so unless a net force acts on it.
-Any object moving at a constant speed or at rest has no net force acting on it.

The hover disc lab allowed us to see how this law works.

With the hover disc turned on, at rest, and not pushed, it will not move because no net force has acted on it yet. Unless person 1 pushes it, it will remain at rest.

We can also see the forces that are acting on the objects. Person 1, 2 and the disc are being pulled down by gravity. But they are not falling through the ground because of the normal force that keeps them up.

With the hover disc on, not being pushed, and moving toward person 2 at constant speed, it will continue to move until a net force is acted upon it. At this moment there is no net force acting upon it which means that it will continue to move. The only way that it will stop moving is when it is stopped by person 2.

We can see the forces acting on person 1, 2 and the disc. They are being pulled down by gravity, but pulled up by their normal force.

Newton's 2nd Law
Force = mass • acceleration

The fan cart lab was a good example of this law.

With a .3 kg fan cart, and a constant force of .298, we measured the acceleration of the fan cart when turned on to high. Later on, we added weights to the fan cart to see how the acceleration would be affected. The sonic range finder allowed us to find the measurements on the computer.

Acceleration is ∆v (velocity) /∆t (time) = a (acceleration)

.3 kg cart: .6518 m/sec. squared

.5 kg cart: .4661 m/sec. squared

.6 kg cart: .4203 m/sec. squared

.8 kg cart: .2848 m/sec. squared

1 kg cart: .1568 m/sec. squared

1.3 kg cart: .1200 m/sec. squared

With this data, we can see that as mass goes up, acceleration goes down meaning they are inversely proportional. We also derived the equation F=ma.

Newton's 3rd Law
When 2 objects interact, they exert equal and opposite force on each other.
-These forces are 1) equal in magnitude, 2) Opposite in direction, 3) The same type of force

From the hover disc lab, when the hover disc is moving and hits person 2's hand, the person's hand and the hover disc both will exert an equal force on each other, force normal.

~ Skydiving

Due to Newton's Laws of motion, this man will continue to move downward because there is a net force acting upon him. The force of gravity is pulling down and nothing is keeping him up because he is not touching the earth. He will have an acceleration because there is a constant force and he has mass. This is why this man will fall with acceleration.