Calculate the average power required by the electric motors

AI Thread Summary
The discussion revolves around three physics problems related to work and power calculations involving electric motors and friction. The first problem involves calculating the work done by a car traveling up a slope with a specified frictional resistance. The second problem focuses on determining the work done against friction for a sliding body on an inclined plane. The third problem requires calculating the average power needed for a mountain railway car traveling between two elevations. The original poster ultimately resolves all questions independently.
shepwarp
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I have three questions that I am pretty confused about:

1. A slope rises 15m veritcally for every 40m of its length (in horizontal direction). A car of mass 1.25t travels a distance of 150m up the slope at uniform speed. Find the work done if the frictional resistance is 40N.

2. A body of mass 0.3kg slides from rest down a plane inclined at 30 degrees to the horizontal. After sliding 30m down the plane it is found to have a speed of 10m/s. How much work has been done in overcoming friction along the plane?

3. A Swiss mountain railway car of the rack and pinion type leaves Zermatt (1608m above sea level) at 9:30am and completes the 9km journey to the Gurnergrat (3136m above sea level) at 10:15am. If the car and the passengers together have a mass of 45t, calculate the average power required by the electric motors (neglect friction).
 
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Please show what you've tried.
 
Never mind! I solved them. :smile:
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

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Thread 'Struggle to understand the concept of the question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
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