A train on a mountain railway is carrying 200 people of average mass 70 kg up a slope at an
angle of 30° to the horizontal and at a speed of 6.0 m s–1. The train itself has a mass of 80 000 kg.
The percentage of the power from the engine which is used to raise the passengers and the train
is 40 %.

What is the power of the engine?
A 1.1 MW B 2.8 MW C 6.9 MW D 14 MW

Question

A train on a mountain railway is carrying 200 people of average mass 70 kg up a slope at an 
angle of 30° to the horizontal and at a speed of 6.0 m s–1. The train itself has a mass of 80 000 kg. 
The percentage of the power from the engine which is used to raise the passengers and the train 
is 40 %. 
 
What is the power of the engine? 
A 1.1 MW B 2.8 MW C 6.9 MW D 14 MW

somy · Answer

what is the answer supposed to be? im getting D

somy · Answer

ouh no i got it its C

anonymous · Answer

It says C.

anonymous · Answer

Oh, I got it too. 6.9 MW. I don't know why I was making it so complicated. Just remembered that I can use the P=Fv formula here. >_<

somy · Answer

yeah thats what i did

somy · Answer

its always like that some we tend to make it more complicated then it already is lol

anonymous · Answer

Yea. :/ Okay guys help me with this one.

anonymous · Answer

great I did that completely on my own

anonymous · Answer

no I mean first question lol

anonymous · Answer

Good. xD

somy · Answer

okaaay lets seee

anonymous · Answer

I'm getting C.

anonymous · Answer

Oh, I just got what I was doing wrong. I was simply multiplying the masses with distances. HOW STUPID of me! -_-

anonymous · Answer

If you multiply C i.e 0.29 with 9.81, you get D 2.8 Nm. 
What is wrong with me today? :'( Earlier, I was using F=mgh.

somy · Answer

how did u do it???

anonymous · Answer

Sum of clockwise moments= Sum of anticlockwise moments

somy · Answer

that's what i did but  i got a weird answer, can u take a pic of ur working plz?

anonymous · Answer

$$6g \times 0.15 + X = (3g \times 0.35) + (1.4g \times 0.1)$$

anonymous · Answer

X is the torque we have to find.

anonymous · Answer

guys why do we take the  component of the speed not the component of the force ?

anonymous · Answer

I don't think you need to worry about that since you're using the formula P= Fv then that means you take the value of the speed from the triangle you draw and then multiply that v with the F

anonymous · Answer

ohright thank you so much 
do you guys take AS level as well ?

anonymous · Answer

yup :)

anonymous · Answer

and no prob :)

anonymous · Answer

Wow , its a pleasure .. :)

anonymous · Answer

WAIT , but why do we divide by 0.4 shouldnt it be time 0.4 ?

somy · Answer

@Lama97 where did u bring 0.4 from?

anonymous · Answer

Im talkig about the first question... like do we multiply by 40\100 or divide >

somy · Answer

i'd suggest you to draw what you are reading 
u'll get a triangle 
it's easier to understand what is going on