Power and Efficiency

Physics Jeopardy

Power and Efficiency

100: A dryer transforms 450 J of electrical energy into 275 J of thermal

energy. Calculate the efficiency of this energy transformation.

200: A cyclist and her mountain bike have a combined mass of 60.0 kg. She is able

to cycle up a hill that changes her altitude by 400. m in 60.0 s. Assume that

friction is negligible. How much power is she able to generate?

Elastic Energy

100:

An elastic band requires a force of 4.5N to stretch to go over a student’s hair. What is the restoring force?

200: The same elastic band in question 1 (4.5 N of force) is stretched a total of 14.0 cm. What is the elastic band’s spring constant?

300: A bungee cord has a spring constant of 175 N/m. If the cord is stretched a distance of 35m, what is the increase in its potential energy?

Energy:

100:

Name the four types of energy we have looked at (not combinations of these) and put 3 of them into 2 main groups.

200:

What law explains this video.

http://www.youtube.com/watch?v=d0HZ9N9yvcU

300:

A roller coaster is shown below. What point has the most potential energy? What point has the most kinetic energy? What point has the most total energy?

400: What is the initial KE of a 0.50 mg flea that leaves the ground at a speed of 30 cm/s?

500: If the KE of a particle is tripled, by what factor has its speed increased?

Conservation Laws

100: Name the 2 conservation laws.

200: Explain the 3 types of systems: closed, open and isolated.

300: Calculate the recoil velocity of a 4.0 kg rifle which shoots a 0.050 kg bullet at a

speed of 280 m/s.

400: A roller coaster is shown below. Assuming that this is an isolated and closed system, calculate the speed of the roller coaster at point D if the speed at point A is 1.8m/s.

500:

Work:

100: What physics term is work the same as?

200: Give an example of each of the 3 types of “no work” scenarios.

300: Determine the amount of work done in the graph below for the first 15m.

400: A 65kg hiker starts at an elevation of 1600m and climbs to the top of a 2800m peak. What is the minimum work required of the hiker?

Momentum and Impulse:

100: What are the two forms of units for momentum?

200: What is the difference between momentum and impulse?

300: Calculate the momentum of a 67. kg rugby player running at 15 m/s [E].

400:

Find the impulse of a 10. kg object that hits the ground with speed of 4.5 m/s and rebounds with the same speed.

500:

A bullet of 0.043 kg is fired directly into a block of wood. Knowing that the bullet left the gun with a muzzle velocity of 375 m/s, and the bullet penetrates 0.125 m into the block of wood (but the wood does not move), determine:

a) The impulse exerted on the bullet by the wood. Explain the direction/sign of the impulse.

b) The average force required to stop the bullet.