Monday, November 19, 2007
Physics Month Continues
We’ve been having a BLAST (sometimes literally) this month exploring force and motion. So far, we’ve explored Newton’s three laws of motion by doing some fun experiments. Are you a bit rusty on ol’ Newton? Here’s a breakdown and some of the hands-on activities we’ve used:
NEWTON’S FIRST LAW OF MOTION:
An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
We tested this law by the “lazy coin” activity. We put a playing card over an empty jar. Then we placed a coin on top of the card and gave the card a quick flick. The card flew off the jar and landed on the table – the coin, however, dropped into the jar. Why? Because the coin is heavier, it has more inertia than the paper does and is harder to move.
NEWTON’S SECOND LAW OF MOTION:
The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
In other words:
If an object is at rest, it is considered to have zero speed. So any force that causes that object to move is an unbalanced force. Any force (such as friction or gravity) that causes an object to slow down or speed up is an unbalanced force.
By building (and playing with) our own hovercrafts, we saw the very real effects of friction and resistance. We also made parachutes of varying sizes and dropped eggs from a high spot. In this last case, we used the entire scientific method – from asking the question, forming a hypothesis, testing and recording. The photograph above shows Megan and Sara before a big launch.
NEWTON’S THIRD LAW OF MOTION:
For every action, there is an equal and opposite reaction.
Newton’s third law was demonstrated by blasting a balloon across a string and making pinwheel rockets.