Energy 1. How much kinetic energy did 93.9-kg Usain Bolt have when he broke the

Question

Energy


1. How much kinetic energy did 93.9-kg Usain Bolt have when he broke the Olympic 100-m dash record with a speed of 10.25 m/s?





2. A 70.0 kg stuntman is attached to a bungee cord. He is standing on a ledge that is 50 m high. How much gravitational potential energy does he have?





3. The stuntman jumps off the ledge and bobs up and down for a while. When he finally stops, the cord is stretched 29 m. If the spring constant of the bungee cord is 71.8 N/m, how much elastic potential energy does the stuntman have?





4. How much gravitational potential energy did King Kong have at the top of the Empire State Building? King Kong had a mass of 25×106 kg. The Empire State Building is 381 m (1,250 feet) tall.





5. A rifle can fire a 4.20-gram bullet at a speed of 965 m/s. Calculate the kinetic energy of the bullet after leaves the barrel of the rifle.





6. In 1992, David Engwall of California used a slingshot to launch at 62 g dart. The dart traveled a distance of 477 m (almost 5 football fields). The amount of potential energy in the slingshot was 140 J. If the spring constant of the slingshot is 30000 N/m, how far was the slingshot stretched?














6. Naim Suleimanoglu of Turkey has a mass of 62 kg (136 lbs), yet he can lift 3 times his mass. This feat has earned him the nickname “Pocket Hercules”. How much potential energy would a barbell have if he lifted the barbell 1.7 m above the floor?





7. Susie Maroney from Australia set a women’s record in long-distance swimming by swimming 93.625 km in 24 h.

(a) What her average speed in m/s?





(b) If she had a mass of 55 kg, how much kinetic energy did she have?





8. A 7.85×1011 kg comet strikes the Earth at a speed of 25 km/s. Which is greater, the amount of kinetic energy this comet had or the amount of energy released by the largest nuclear weapon ever built (4.2×1015 J = 100 million tons of TNT)? Such a comet collision has been suggested as having caused the extinction of the dinosaurs.

Explanation / Answer

1.
KE = (0.5)( 93.9kg)(10.25m/s)2

KE = 4932.68 J

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