pool

This weekend I went swimming in a pool. I jumped in and with no surprise, I felt much lighter. This was due to the buoyant force. The volume of the displacement of pool water multiplied by the density of pool water and gravitational force was equal to the buoyant force. My weight minus the buoyant force was equal to my weight in the pool.
If I floated instead of sunk in the pool, then the buoyant force would be equal to my weight.

spoon levers

I was eating ice cream when I noticed that using a spoon required physics. The a scoop of frozen ice cream needed to be pried with force from a spoon. By using the side of the bowl as a fulcrum, I applied a downward force with my hand. Once there was enough force to overcome the static friction force of frozen ice cream, the small scoop was lifted. If I moved the handle of the spoon farther away from the fulcrum, it would have made lifting the ice cream easier since less force is necessary because the distance between the fulcrum and my hand increases and the distance between the fulcrum and the ice cream decreases. If the handle of the spoon is closer to the fulcrum it will be harder to lift the ice cream.

Dizzy

So I was sitting on my chair in front of the computer not knowing what to write about for this weeks journal entry. I began to spin in the rolling chair and I realized that that was actually physics. I stuck both of my feet out parrallel to the ground and although it was moving at the same angular velocity, their tangential velocity was more because the radius from my toe to the center of the chair was larger. I began to spin faster and faster. My toes now had a higher tangential acceleration but the same angular acceleration. I began to count in radians the number of spins that I could do. 2 pi, 4 pi, 6 pi, 8 pi, 10 pi, 12 pi . . .



no that is not fire. This is turning into a biology blog.

Jumping in Sand

Why is it harder to jump higher in sand than it is to jump on a court? This is the question I began to ponder as I grew exausted from playing beach volleyball. I then realized that Newton's Laws were the reason for my exaustion. In order to jump, the legs need to exert a force on the ground so that the ground exerts and equal and opposite force to push the body in to the air. In the gym, nearly all of the force exerted by the floor is transfered to the jump. On the beach however, tiny sand particles cushion the force of the jump by spreading outward. Therefore not a lot of the force is transfered to the jump because some force is needed to push the sand particles outward. The static friction of the sand is also relatively small compared to the solid, one-pieced court.