M2 Work and Energy help

mathsexam2013

A bus of mass 8 tonnes is driven up a hill on a straight road. On one part of the hill, the power of the driving

force on the bus is constant at 20 kW for one minute.

(i)
Calculate how much work is done by the driving force in this time.
[2]

During this minute the speed of the bus increases from 8 m s–1 to 12 m s–1 and, in addition to the work done against gravity, 125000 J of work is done against the resistance to motion of the bus parallel to the slope.

(ii)
Calculate the change in the kinetic energy of the bus.
[3]

(iii)
Calculate the vertical displacement of the bus

Hi, just need some help on part 3 of this question
The answers to the first two parts are 1,200,000J and 320000J increase

any help

Original post by mathsexam2013

any help

KE_A + PE_A +WORK_in - WORK_out = KE_B + PE_B

Reply 3

mathsexam2013

yes, but how do you work out PE with the information theyve given

Reply 4

TeeEm

Original post by mathsexam2013

yes, but how do you work out PE with the information theyve given

You rearrange the equation I gave you to PE_B - PE_A = ... the rest onto the other side ...
the "right hand side quantities" are all known

thus difference in PE can be found

So mgh = ....

I think the question merely asks for vertical displacement h