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## Homework Statement

1. A 1000kg car has a 50kW engine and is traveling at 60 kilometers per hour-

a) solved!

b) calculate how much work is done by the engine during this time

c) calculate what the force being exerted on the car during this time

2. Determine the energy used to operate a 240V water heater continuously for four hours. The resistance of the element is 12 ohms.

## The Attempt at a Solution

For b, I feel the only way to get the answer is by finding out how much energy is required to keep a car going at 60kmp/h (neglecting friction/wind)- but only f=ma comes to mind which is useless as there is no acceleration. To find the work (energy), I would need to find the force required right? Work= Fd

For c, I'm quite stumped. I can't think of what equation I need to solve it.

For 2, I've worked everything except the last.

First I solved for I(amperes)

I=V/R --> 240/12 = 20A

then

P=IV --> 20.240 = 4800W

Now, it's asking how much energy (power/Watts) is used in 4 hours. With the result of 4800W, do I just times it by 60x60x4?? Is 4800W used in a second, a minute or an hour? I'm not entirely sure.

Cheers for any help! It will be very much appreciated!