Question

1. What is the main difference between a conventional internal- combustion engine and a Diesel engine?

2.A rocket engine operates more efficiently in the absence of air. Why?

3.A 10-ton truck travelling at 20 m/s is brought to a stop by the brakes. How much heat is produced?

Given:

m = 10 tons = 10,000 kg , v = 20 m/s  

J = 4.18 joules/calorie, W = 2 X 106 joules

Answer 1

1) The main difference between a conventional internal- combustion engine and a Diesel engine is that in a disel engine the air-fuel mixture is not ignited by a spark plug, insted the mix is ignited during compression stroke by the pressure created by the piston.

2) Wind produces resistance agaist motion of a rocket. In an airless environment this resistance is null. So the entire thrust of the rocket is converted into the forward kinetic energy.

3) The entire kinetic energy of the truck is dissipated as heat by the friction of the applied brake.

Kinetic energy= ,

According to Joule's law, the amount of heat generated= H =