# Fun Gravity Experiments

## Main Principles

• To see the main principles of gravity at work -- that it pulls all objects towards the earth -- use a plastic cup, some water and a pencil. Poke the pencil through the cup at the bottom and then fill it with water and see what happens. Refill the cup with water and as the water is pouring out the cup drop the cup and see what happens. The water should stop pouring out as the cup heads towards the ground. The reason is because when the cup is being held gravity is acting on the water pushing it down towards the earth. When the cup is dropped, gravity is acting on both the cup and the water at the same time with the same pressure meaning no water is forced out.

## Center of Gravity

• The center of gravity is the point at which the weight on either side of the object is the same. It is the point of the object where gravity has the most impact. There are a number of experiments which will enable you to find out where your center of gravity is. One is called superglue chair and it requires you to sit in a chair with your back straight against the back of the chair and your feet flat on the floor. Try to get up without moving your back forward and you'll find you can't. This is because when you sit, your center of gravity is in the base of your spine and to get up, you need to move it forward so that it is above your feet. By trying to stand up with your back straight you prevent this from happening, which means you cannot stand up.

## Gravitational Acceleration

• We know that gravity pulls everything down towards the earth, but does it pull heavy objects faster than lighter objects? To find out, the scientist Galileo carried out an experiment in which he dropped two objects of different weights from the same height and recorded the results. You can carry out the same experiment by standing on a chair and dropping an orange and a grape at the same time from the same height. Have a friend lie on the floor so they can record which hits the floor first. You should notice that they hit the floor at the same time, as gravity makes all objects accelerate at the same speed regardless of their weight.

## Velocity on Gravity

• The speed at which something moves has an effect on the forces of gravity as explained by Sir Isaac Newton's Universal Law of Gravitation. The faster something moves the less effect gravity has on it. This principle can be carried out by taking an empty jar and a rubber ball. Place the rubber ball in the jar and place the jar flat over a table. Then start spinning the jar around in a circular motion making sure it remains on the table. The ball should move up the sides of the jar. Stop spinning the jar and the ball loses its speed and the forces of gravity pull it back down to earth.