. A 5 gram bullet is moving at 400 m/s. It passes through a 2” thick piece of wo

Question

. A 5 gram bullet is moving at 400 m/s. It passes through a 2” thick piece of wood and comes out moving at 300 m/s. How much heat energy could have been generated? What was the average force on the bullet?

5. What is the KE of a 200 lb man on a 35 lb bicycle moving at 20 mph? If it took him 10 seconds to get to 20 mph, what was his power output?

6. According to the 1967 Journal of Experimental Biology paper “The Jump of the Flea: A Study of the energetics and a model of the mechanism” by Bennet-Clark and Lucey, when a flea (mass 0.45 mg) jumps it accelerates from 0 to 1 m/s in approximately 0.85 ms. Determine its acceleration and power.

7. A 2000 kg car moving at 20 mph plows into the back of a 10,000 kg truck that is standing still. The wreckage sticks together after the crash. How fast is it moving?

8. Re-work the above problem, this time with the car standing still and the truck moving at 20 mph.

9. A swimmer dives off the stern of a pontoon boat that is at rest. What will the boat do? What if there are five other adults on the boat?

10. In the above problem, what if the boat is a huge coal barge? Is momentum still conserved in this case?

Explanation / Answer

m = 5 * 10^-3 Kg
Vi = 400 m/s
s = 2'' = 0.0508 m
Vf = 300 m/s

Heat Energy Generated = Lost in Kinetic Energy
Heat Energy Generated = 1/2*m*[Vi^2 - Vf^2]
Heat Energy Generated = 1/2 * 5 * 10^-3 * [400^2 - 300^2] J
Heat Energy Generated = 175 J

Force on the bullet, = m*a

Where a is,
V^2 = u^2 - 2*a*s
300^2 = 400^2 - 2*a*0.0508
a = 688976 m/s^2

Force on the bullet, F = 5 * 10^-3 * 688976 N
F = 3445 N

please post seperate questions in seperate post only.

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