Impulse Lab

In this lab, we used two metal rings attached to 2 carts with a force probe to explore the relationship between time, force, and impulse in a collision.

Impulse is defined as a change in momentum. But how doe we measure change? Let's say that you go to the Giants World Series game with $100 dollars in your pocket. During the game, you buy a coke, cotton candy, popcorn, and a sweatshirt. The total cost of the novelties is $50. Since you spent $50, the change would be recorded as -$50. It is expressed in the following equation:

Change (delta) = end - start

Impulse = the momentum after a collision - the momentum before the collision (addressed as a negative because momentum is a vector)

The relationship between force, time, and impulse is also expressed in an equation:

J (impulse) = F (force) x t (time) or J= deltaP = P(after)- P(before)

According to Newton's Third Law, for every force, there is an equal and opposite force.

in a collision, the impulse is always the same because time and force are inversely proportional, meaning that if the force increases, the time during the collision decreases and vice versa.

For example, a boy is jumping off of a table. When his feet collide with the ground, his knees instinctively bend. By bending his knees, the boy allows the collision to last longer, making the force of the collision smaller on his body. If the boy had collided with the floor with his knees locked, the collision would have happened faster (less time) and the force on the boy's legs would be greater. The bones would not be able to absorb the amount of force and unfortunately, his bones would break but no matter how the boy lands, the impulse of the collision would remain the same.

Real World Connection:

There is a reason why airbags are installed in every modern car. Collisions involving automobiles are particularly lethal to humans. In accidents, the airbag increases the amount of time that a human body comes in contact with the steering wheel, making the force of the collision smaller on the human body and saving millions of lives.

Rubber Band Cart Launcher Lab

This week, the purpose of the lab was to discover the relationship between velocity and energy. In addition, we were also supposed to find out what kinetic energy was and how it is used in an equation.

In order to answer these quesstions we used a red cart, a Photogate sensor that measured the velovicy of the cart, a rubber band, and an air-filled ramp that helped eliminate friction so that we could accurately measure the velocity. Our table stretched the rubber band (doing work) and the cart from .01-.05 meters and released the cart down the ramp. The censor measured the velocity of the cart for each trial and then we repeated the expiriment.

From the data that we collected, we noticed that as the energy (work) increased, the velocity of the cart increased. In other words, the farther we stretched the rubber band, the faster the cart moved.

Key information:

*energy cannot be destroyed! It can only change forms. (transferred from one form to another)
work-->spring potential energy-->kinetic energy (energy in motion)
*The slope of kinetic energy is 1/2 the mass. Since the car was .4kg, the slope is .2 kg

KINETIC ENERGY EQUATION:

K = (1/2m)(v^2)
Y= (m)(x) +b
K=kinetic energy
m=mass (kg)
v=velocity squared (m/s)



LOL charts (as seen below) help us distinguish the transfer of energy from one form to another

L= energy that we start with
O= objects involved
L= energy that we end with


Real World Connection:

What we learned in class this week relates to the concept of trampolines. Energy and velocity are related just as the rubber band relates to the cart. In this case, The trampoline is like the rubber band and the person jumping resembles the cart. We do work when we jump on the trampoline and the nylon material stretches to support our weight. The more the nylon surface is stretched, the more energy is stored, whih means that we will jump faster and higher when the energy is released.