Air track, two gliders (one heavier than the other), force spring, 500g-weight, timer, ruler, paper, two carts, masking tape. Background Theory: Momentum ? = mv – Momentum is conserved in a closed isolated system (no external forces) – Kinetic energy is conserved in an elastic collision – Inelastic collision- stick together Inelastic collision: Before: After: Elastic collision: Before: After: Cart Explosion: Before: After: Procedure: Part I: Inelastic and Elastic Collisions 1. Set up an air track with two gilders of different masses on it. 2.Tape cardboard to the gilders so that the timers can read them, measure the lengths of the cardboard and record in Table 1. 3. Weigh the gliders and record in Table 1.
4. In the inelastic collision, the smaller glider is at rest, gently push the larger glider so that it sticks onto the smaller glider across the timer with minimum space in between. Repeat this step 3 times, and record the times in Table 2. 5. In the elastic collision, the larger glider is at rest, gently push the smaller glider so that it hits the larger glider and both bounce back and through the timers. Repeat this step 3 times, and record the times in Table 3.Part II: Cart Explosion 1.
Measure weight of the two carts and the weight used using a force spring. Record the measurements in Table 1. 2. Place weight on one of the carts.
3. Push the springs of the two carts as closely together and release, start timing. 4. Time both carts using different timers, stop timer when cart stops moving. 5.
Measure the distances the cart travels with a meter stick, record measurements in Table 4. 6. Repeat steps 1-5 three times.
Observations and Analysis: Table 1 Measurements Mass (if applicable) Length (if applicable)Gain of Kinetic Energy Undefined Undefined Conclusions: The lab that we did demonstrated to a certain extent the conservation of momentum and kinetic energy in elastic and inelastic collisions. As shown in the analysis of the inelastic collision (Table 5), the data worked fairly well and there was little discrepancy between the value obtained in the lab and the theoretical value, amounting to 3. 3 i?? 0.
9%. However, the same cannot be said for the elastic collision on the air track. As shown in the analysis above, there was a whopping 57% i?? 1% gain in momentum, when the theoretical value is none!As for the cart explosion, despite various factors such as friction between the floor and the cart wheels, cart not running in a straight line, reaction time when timing etc, the data worked out fairly well, to my surprise. As shown in Table 7, there was yet again minimum discrepancy: 0. 33 i?? 0.
03 kgm/s. In conclusion, this lab had only limited success in showing the conservation of momentum and kinetic energy. One aspect that still puzzles me is the large gain in momentum in trial 1 of our elastic collision lab, may it be a faulty operation and should have been seen as an anomoly I have yet to find out.
Sources of Uncertainty:When doing the cart explosion, we found that the cart rarely travelled on a straight line. This could be due to factors such as friction, position of the cart on the floor and position of the weight on the cart. The existence of this uncertainty resulted in our data being somewhat off. In future experiments, we shall attempt to limit this by aligning the cart with a meter stick or such.
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