# Need help with problem please

a car is driven at a constant speed of 76km/h down a road. The car's engine delivers 48 kW of power. Calculate the average force that is resisting the motion of the car

any help would be appreciated. I had an idea, but i dont know if its right.

## Answers and Replies

Curious3141
Homework Helper
What is the relationship between Power, force and velocity ?

well i was thinking power=w/t, so power=fd/t, d/t is velocity, so power = force x velocity, and i figure out that force. it is asking for resisting force, so it is asking for the frictional force. Since it is constant speed, the net force is zero, so it would just be the negative force of the above force. This is what i was thinking

Curious3141
Homework Helper
Well, there you go. Another way to look at it would be that all the engine's power is going to overcome friction. This is why the car is not accelerating.

Last edited:
thats right?

brewnog
Science Advisor
Gold Member
Yup yup!

Hmm, 'yup yup!' is too short, so I had to add this bit.