Impulse Lab

Introduction
In this week's lab we crashed an empty red cart into a force-probe with aluminum (to slow down time) attached to a ring stand. We found the velocity of the cart before and after the collision. We then found the change in momentum, also known as impulse. We did this to measure the relationship between impulse, force, and time during a collision.

cart with aluminum

force prob with aluminum

Key Info

• impulse: a change in momentum (another way of representing the conservation of momentum)
• impulse is measured in Joules

• momentum = P

• impulse equation: J = Pfinal - Pinitial

• mass of car: 0.25 kg

• velocity is measured in meters per second (m/s)

Big Question

What is the relationship between impulse, force, and time during a collision?

After we collided the car with the aluminum ring, we found the velocity of the cart in the collision before and after using the sonic range finders. Then we found the momentum before and the momentum after to find the impulse. Then we recorded the area, also known as the integral, under the Force vs. Time graph. 



Here is what our data looked like:

From here, we did the calculations and found that the area of a force vs. time graph is impulse. So now the equation for impulse can be written as Impulse = Force (Time) or J = F(t).

Analyzing Data

Concluding Ideas
       Impulse and Are are the same! After determining the area of a Force vs. Time graph and calculating the impulse, the answers come out to be equal. Forces are equal and opposite; therefore, the impulse remains constant in a collision by increasing the time and decreasing the force. In the collision, the metal sheets increased the time and decreased the force.

Real Life Connection
        Boxing uses this same principle of minimizing the effect of a force by extending the time of the collision. When a boxer recognizes that he will be hit in the head by his opponent, the boxer often relaxes his neck and allows his head to move backward upon impact. This known as "riding the punch." A boxer rides the punch in order to extend the time of impact of the glove with their head. Extending the time results in decreasing the force and then minimizing the effect of the force in the collision. Now that is physics in action!
  
Here's a clip from the final fighting scene in the movie Rocky Balboa