Mechanical Power

Question 1

What does Power equal? (3)

Answer 1

P=E/t or P=W/t or P=Fv

Question 2

What is the SI base unit for power?

Answer 2

kgm^2s^-3

Question 3

What is more efficient than a filament lamp?

Answer 3

An LED

Question 4

What does Efficiency equal?

Answer 4

Useful energy out/total energy in (x100)
or
Useful power out/total power in (x100)

Question 5

Define Power.

Answer 5

The rate of work done/energy with respect to time.

Question 6

Define 1 Watt.

Answer 6

I joule per second

Question 7

What is the resultant force is an object is travelling at a constant speed?

Answer 7

0, therefore the total forward force must equal the resistive force.

Question 8

How do we derive P=Fv?

Answer 8

1) Power =W/t
2) Power = force x (distance/time)
3) P =Fv

Question 9

What can efficiency be expressed as?

Answer 9

A percentage or a number between 0 and 0.1

Question 10

Why is most mechanical systems less than 100% efficient?

Answer 10

Because of thermal losses caused by frictional losses.