Work and Energy Problems [help]

[krypt0nite]

1) How much work does it take to accelerate an electron(mass=9.11x10^-31kg)
from rest to a speed of 5.0x10^6 ms?

I know you have to use more than 1 equation to solve it but I can't seem to get close to an answer.

2) How much work must be done to stop a 1000-kg car travelling at 100km/h?

Is it me or does this question not have enough info.

[Doc Al]

Is it me or does this question not have enough info.
It's you. :smile: Remember that work done on an object equals its change in KE.

[krypt0nite]

2) How much work must be done to stop a 1000-kg car travelling at 100km/h?


KE = 1/2mv^2
KE = 1/2(1000)(27.278)^2
KE = 385809 Joules
So the work to stop it would be that much?

[krypt0nite]

And I assume the 1st question is done the same way?

[Doc Al]

KE = 1/2mv^2
KE = 1/2(1000)(27.278)^2
KE = 385809 Joules
So the work to stop it would be that much?
That's the idea. (Check your conversion of 100km/hour.) (Don't state so many significant figures in your answer.)

And, yes, the first problem is the same idea.

[krypt0nite]

That's the idea. (Check your conversion of 100km/hour.) (Don't state so many significant figures in your answer.)

And, yes, the first problem is the same idea.
Thanks SOO MUCH!