Dec. 7-11

This week, we continued to learn about force. We were given problems for homework, and in class we would discuss it. One of the problems was that an elevator had a negative amount of force pushing down on it, and we had to explain whether it was speeding up or slowing down. It turns out that it can be either because total force actually represents acceleration. If the elevator was going up, it would be slowing down, and if it was going down, it would be speeding up. The unbalanced forces in a forc e diagram are like the delta v arrow in a motion diagram. If it isn't moving and the forces cancel out, it isn't moving. if it is moving and the forces cancel out, it isn't accelerating. If an object is moving horizontally, and not vertically, and the vertical forces cancel out, it is not moving vertically, and vice versa.

We also learned from pushing people on carts that mass also affects acceleration. when there was only one person on the cart, the acceleration was greater than when there were 2 or 3 people on the cart. The two hypotheses that we had were that as mass increases, acceleration decreases, and when m decreases, a increases. The other hypothesis was that as m increases, a increases, and as m decreases, a decreases. They are both right. The first hypothesis is correct if the force each time is the same, like someone pushing. The other is true if the amount of force on the object depends on the mass, like the force of the earth. If the mass is greater, the force is greater, making it accelerate faster.

This would be useful if you are racing someone on a cart because you would want less mass on your cart so that there would be greater acceleration. And if you are jumping off something and seeing who gets to the bottom first, the heavier person is gonna get there first.