Question

The force resisting the motion of a car is taken as being proportional to the square of the car’s
speed. The magnitude of the force at a speed of 20 m s–1 is 800 N.
What effective power is required from the car’s engine to maintain a steady speed of 40 m s–1?
The Available Answers Are:
A 32 kW B 64 kW C 128 kW D 512 kW
And C Is The Correct Answer.
Just Need To Find How It Is Solved.

Answer 1

hi Julian!! i can help u: 1) F=\[F=\alpha*V ^{2}\]
so \[\alpha=F \div (v ^{2})\]
\[\alpha=800\div 20=2kg.m ^{-1}\]
\[P=W \div t=(F \times d) \div t=F \times v\]
\[F=(2kg.m ^{-1})\times (40m.s ^{-1})^{2}=3200N\]
and finally \[P=40m.s ^{-1}\times3200=128000Watts=128KW\]
i hope this helps, graduated from school long time ago n took me a bit to remember stuff :)

Answer 2

be careful for units always

Answer 3

thanks alot pal you saved me? may the force be with you! XD

Answer 4

!*

Answer 5

ur welcome :) n gd luck