OCR A level mechanics (M1) Chapter8 Work, energy, power 5 questions HELP

[yanb0706]

OCR A level mechanics (M1) Chapter8 Work, energy, power... 5 questions HELP!

2. A winch is used to raise a 200 kg load. the maximum power of the winch is 5 kW. Calculate the greatest possible acceleration of the load when its speed is 2m/s, and the greatest speed at which the load can be raised.

5000/2=2500N
2500/200= 12.5 m/s^2 ??

Answer: 8.2m/s^2 2.55m/s

3. A pump, taking water from a large reservoir, is used to spray a jet of water with speed 20m/s and radius 0.05 metres, from a nozzle level with the surface of the reservoir. Calculate the power of the pump.

Answer: 31.4 kW

4. A crate of mass 5 kg is pulled directly up a rough slope, of inclination 10 degrees, by a constant force of magnitude 20N, acting at an angle of 30 degrees above the horizontal. Find the work done by the force as the crate moves a distance of 3m up the slope.


Answer: 56.4W

5. A barge is pulled along a straight canal by a horse on the towpath. The barge and the horse move in parallel straight lines 5m apart. The towrope is 13m long and it remains taut and horizontal. The horse and the barge each move at a constant speed of 0.78m/s and the towrope has a constant tension of 400N. Calculate the work done by the horse on the barge in 10 minutes.

Answer: 173kJ

btw, I don't know when to use P=FV and P=FS/t . What's the difference between them?


REALLY APPRECIATE THE HELP THX!

 

[member 553083]

Answer: P=FV is used for calculating power when a constant force is applied to an object and it moves with constant velocity. P=FS/t is used for calculating power when a constant force is applied to an object and it moves with changing velocity (acceleration).