Question

1. There was a car accident. Someone stopped and the person behind them rear ended them. The car that stopped slid away about 30 feet and the car that did the rear ending stopped right about where the collision happened. Was this a perfectly inelastic collision? Why or why not?

2. A perfectly elastic collision is one in which kinetic energy is conserved. How exactly is kinetic energy not conserved though? Sometime KE can be used up compressing/bending things and making heat, or becoming sound, or even something more exotic like causing a material to change phase. In the car accident in question 1, the front of the car was mashed up and leaking fluids on the ground. Do you think this was a perfectly elastic collision? Why or why not?

3. You are an astronaut on Mars (which has no air resistance) whose job is to discover the crash site of a payload. The payload was encased in a rocket composed primarily of two parts. The speed before the explosion is known to be 250m/s, it’s direction was known to be north, it was cruising at 2000 meters above the surface, the fuel level was 5 gallons, and the total mass of the rocket (neglecting the tiny payload) was 700kg. The most forward part of the rocket has been discovered on the surface and has been measured to have a mass of 500kg, but the location of the payload is unknown. If you can find where the explosion occurred, the payload will be nearby because of its parachute.
   250 m/s 2000m
   

1. The rocket fuel has an energy density of 1E8 Joules/gallon. How much energy was in the explosion?

2. First neglect the fact that the rocket was traveling at 250 m/s, imagine it was stationary or that you were flying alongside it. The explosion has certainly occurred so that the forward part was launched North and horizontally. Now write down the conservation of momentum for this problem using variables for what you don’t know yet. Hint: remember velocity has a +/- sign depending on direction!

Extra Hint: P_initial=P_final

3. now assume all the energy of the explosion went into kinetic energy, write down the equation relating the velocity of the two parts of the rocket and the energy from the explosion. Again use variables for terms you don’t know.

4. Now use these two equations to solve for what the velocity of the 500 kg piece must have been.

5. Calculate how long it would take for this forward part to fall to the ground. Gravity on mars is about 3.11 m/s^2

6. Now using the time you calculated in part e, the velocity you found in part d, and the original 250 m/ s of the rocket figure out roughly how far away is the payload and in what direction?

Now using the time you calculated in part e, the velocity you found in part d, and the original 250 m/ s of the rocket figure out roughly how far away the payload is and in what direction.

Answer 1

3 ofect accident Spot No this was not a perfectly inelastic collision because in perfectly inelastic collision the boelies Stick together after the collision and move as a single kot energy is not conserved in this case because due to collision Shape of cars has changed and also lot of sound and friction is produced so energy is lost in this form and this lost energy is provided by the only energy present which is kinetic energy of cons. No this was not a perfeelly classic collision because Kinetic energy is not conserved here durines the collision.

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