Calculating GPE and Power for a Cable Car Ride

[james_rich]

Hey just gettin a bit stuck on this question...i'll attempt to answer it, but it really doesn't look right to me.

A cable car is used to carry people up a mountain. The mass of the car is 2000kg and it carries 80 people, of average mass 60kg. The vertical height traveled is 900m and the time taken is 5 minutes.

i) Calculate the gain in GPE of the 80 people in the car

GPE = mg/\ h

= (80 x 60) x 9.81 x 900

= 4.2 x 10^7 J

Is this right so far?


ii) Calculate the minimum power required by a motor to lift the cable car and its passengers to the top of the mountain.

Power = Work Done/Time Taken

Work Done = Force x Distance = (4800 + 2000) x 9.81 x 900
= 6.0 x 10^7

Power = (6.0 x 10^7) / 300 (as 5 mins = 300s)

P = 2.0 X 10^5 watts


These are the answers I got...i think I've used the right method, just need some reassurance!

Thanx in advance!

 

[Nylex]

Working looks ok to me.

 

[wais]

Your calculations look correct to me! Good job on using the formula for GPE and power. Just a small note, the mass of the car should also be included in the calculation for GPE, so it should be (4800 + 2000) instead of just 4800. Other than that, great job! Keep up the good work.