The Changes and Conservation of Momentum in a Two Cart Explosion

Momentum (P) is the product of an object’s mass and velocity (Id. mind. net). Momentum is dependent on velocity, thus it is a vector quantity, meaning it has magnitude and direction. In accordance to the Law of Conservation of Momentum, the total momentum of any group of objects remains constant unless acted upon by outside forces (Straub). In an explosion, there exists an internal impulse (J) which is defined as a change in the momentum. The impulse ( J = Force x Time) during the explosion sends different parts of the object into many different vectors. When all the vectors are added together,

the final momentum should equal the initial momentum. An isolated system is a physical system that does not interact with its surroundings such as air resistance and friction. In an isolated system total system momentum is conserved, proving that the final momentum should always equal the initial momentum. In an explosion, the objects may start from rest. After the explosion, according to the Law of Conservation of Momentum, the objects that moved in opposite directions should end at rest (Regentsprep. org). The law of conserving momentum in an explosion can be tested by using spring carts with different masses.

By adding/subtracting their masses, the velocities of the carts will change, which will affect the final momentum of the carts. By altering the momentum, the system final momentum will also be changed in some way (Straub). However, if the system of an explosion is isolated, then the final momentum should equal the initial momentum, zero. Methods and Procedures: The materials needed are as follows: two spring carts, 3 bricks with different masses, a stop watch, and a meter stick. A spring scale and string will be used to weigh the carts and each of the bricks. A flat surface will also be necessary.

First, hang one of the carts on the hook of the spring scale. Record the cart’s mass in kilograms. Repeat this step for the second cart. Next, tie a piece of string around each brick so they can be weighed using the spring scale. Record each of the masses of the bricks. Then, place the carts on a flat surface, such as a desk. To load the exploder, push the cylindrical rod into the cart and pull upwards. Place the second cart in front of the first so that the spring from the first cart will explode into the second cart. Lay the meter stick down beside the carts to measure the distance the carts move. To release the

exploder, push down the pin at the front of the cart. Initiate time as soon as the spring from cart one is released. Record the time and distance where the first cart stops. Flip flop the carts’ positions and reset all previous steps. Now repeat the steps so that you are recording the time and distance of the second cart. Place the first brick on cart 1 and load the exploder. Place cart 2 in front of the first so that the cart with the brick is pushing off the empty cart. Record the distance the cart has traveled and the time it took to get there. Now switch the carts positions so that the empty cart is pushing off the cart with the brick.

Record time and distance again. Place the first and second brick on cart 1 and set the second cart up so that the cart with the bricks is pushing off the empty cart. Record distance and time. Switch the carts around again so the empty cart is pushing off the cart with the bricks. Place all three bricks on the first cart and place the second cart in front of it. Like the previous trials, set the cart up so that the cart with the bricks is pushing off the empty cart. Record distance and time. Now switch the carts to record cart 2’s data. Place brick 2 on cart 1 and brick 1 on cart 2. Switch the carts and record the data of cart 2.

Finally, place brick 3 on cart 1 and brick 1 and 2 on cart 2. Set up the carts up so that cart 1 is pushing off cart 2. Record distance and time. Then switch the carts to record cart 2’s data. The velocity of each cart can be calculated by dividing the carts distance traveled by time. After finding each carts velocity, multiply that quantity by their mass to find final momentum. Since all the carts began at rest, the system initial momentum for each cart will be zero. After calculating the momentum for carts 1 and 2 in each trial, subtract the final momentum of cart 1 from final momentum of cart 2 to calculate the system final momentum.