Hi guys. Need a little help with an IB paper(Just two questions!) and would really appreciate your help.(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

A bus is travelling at a constant speed of 6.2m/s along a section of road that is inclined at an angle of 6.0 degrees to the horizontal.

State the value of the rate of change of momentum of the bus.

b) The total output power of the engine of the bus is 70kW and efficiency of the engine is 35%. Calculate the input power to the engine.

c) The mass of the bus is 8.5 x 10^3 kg. Determine the rate of increase of gravitational potential energy of the bus.

d) Using the answer to c and data in b, estimate the magnitude of resistive forces acting on the bus.

2. Relevant equations

p=mv.

a= g sin theta.

F= ma.

GPE = mgh.

SUVAT equations.

3. The attempt at a solution

a) As it is constant speed, zero net force. Zero net force, zero momentum. Answer is zero.

b) Output power is 70000/x * 100% = 35%. Solving for x yields x=200000W.

c) Velocity is 6.2 m/s at a 6 degree incline. 6.2 sin 6 gives me the vertical component of velocity, 0.648 m/s. Rate of increase of GPE is mgh/t, so 8.5*10^3*9.8*0.648 = 54000 J.

(Is this right?)

d) No idea. @_@ Can someone lead me in the right direction?

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# Homework Help: How can you find the rate of change of momentum?

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