Impulse Lab

• In this weeks lab, we did an experiment to answer the question What is the relationship between impulse, force, and time during a collision?
• Before the lab, we knew that impulse (J) can be defined as a change in momentum (p_after - p_before).
• Our general procedures of the lab started by crashing an empty cart into the force-probe attatched to the ring stand. we then recorded the carts velocity before the collision and then after the collision. These points are shown in the bottom half of the picture below. Then we found the area under the Force vs. Time graph by highlighting the green trianguar shape shown below.

• Then we calculated the impulse of the cart and this work is shown in the whiteboard that we did in class below. 

• We were also asked how the impulse and the area under the Force vs Time graph compare? By comparing the integral (area of the proabola) and the impulse that we calculated, we saw that after considering there may be minor error in our experiment, that the integral and impulse are the SAME! From this information, we went through the following process to derive the equation below.

• We also noticed that the impulse on an object in a collision is constant. This means that force and time are inversely proportional. Forces are equal and opposite.

• This just sounds like a bunch of useless scientific facts, but it actually really makes sense. In field hockey, one is supposed to "give with the ball" when they receive it. This means that when someone passes to you, you don't just stick out your stick because then the ball will bounce off and will no longer be in your possession. By increasing the time before the ball and stick make contact, the force of both decrease. See this in action in the video below!

Collisions Lab: Momentum

• In this weeks lab, we measured the patterns in velocity when two things collide. we did this by having two carts, both .25 kg, collide with each other. We did trials with elastic, and inelastic collisions. For the elastic collision, the cart's spring launchers were facing each other which made them bounce away from each other after they collided. During the inelastic collision, the cart's Velcro ends were facing each other, causing them to stick together and stop moving. A picture of our inelastic collision, BEFORE the collision, is shown below:

We defined momentum as mass in   motion, giving us the equation: p=mv

• After we calculated everything and filled out the chart to the right, we were asked to find the amount of Momentum (p) and Kinetic Energy(KE or just K) that was lost during the collision to our surroundings.
• For the elastic collision, 19.61% of the kinetic energy was lost to surroundings, and only 1.71% of momentum was lost! In the inelastic collision, more kinetic energy was lost compared to momentum as well. 
• From this, we concluded that in a collision, energy is often lost to the surroundings, but momentum is conserved. 
• P total before=P total after

ENDURING QUESTION:

• Why is it that in the inelastic collision, the carts came to a standstill when they collided?

Remember above when i said that momentum is conserved, therefore the momentum before and after a collision are the same? Well if we break down momentum (p) into mass (m) times velocity (v), and recognize that a cart moving to the right has a positive momentum, and a cart moving to the left has a negative momentum, we could conclude something like the picture below: 

REAL-WORLD CONNECTION:

This lab made me think of playing pool, considering there is more than one ball and they collide on the table all the time. If i were to hit a pool ball with my pool stick, this ball would have momentum. Then when this ball is moving across the pool table with a certain velocity and collides with another pool ball, both of these balls now have momentum because the momentum from the first ball was transferred and conserved.  Considering these balls are not going to stick together, the balls will most likely move apart from each other.