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
Messages
7
Reaction score
0
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).
 
Physics news on Phys.org
Please show what you've tried.
 
Never mind! I solved them. :smile:
 
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Thread 'A cylinder connected to a hanged mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top