A car weighing 6600 N moves along a level highway with a speed of 110 km/h. The power of the engine at this speed is 57kW. The car encounters a hill inclined at an angle of 9.1 with respect to the horizontal.
If there is no change in the power of the engine, and no change in the resistive forces acting on the car, what is the new speed of the car on the hill? Answer in units of km/h.
I am so confused on this problem, can anyone step me throught it and help me get an answer.
2006-11-03 18:25:22 · 4 answers · asked by polo_05_polo 1 in Science & Mathematics ➔ Physics
The power needed to keep the car moving is P=F*v, where F is the force applied and v is the velocity. (Work = F*s; power is work per time = F*s/t; s/t=v, so power = F*v). To keep the units straight, convert the velocity from km/hr to m/s, since 1W = 1N*m/sec. 110km/h = 110*10^3/3600 m/sec = 30.56 m/sec. The power is then P= 30.56*F. You are given the power, so you can find the resistive force on the car F = 57*10^3/30.56 = 1865.2N. When the car reaches the hill, the force increases by m*g*sin(ø) = w*sin(ø). (Draw a diagram of the car on the incline; the weight of the car acts straignt down; the component of weight along the incline is that times sine of the incline angle.) So now the power has to drive 1865.2 + 6600*sin(ø) N. The power is the same P = 57kW, but the force is different, and we know it. Solve for velocity from P=F*v, where F is now the increased force (1865.2+6600*sin(9.1º).
2006-11-03 18:54:34 · answer #1 · answered by gp4rts 7 · 0⤊ 1⤋
there will be resistance. I think it is the sine of the hill at 9.1 degrees relative to the effect of gravity which increases the load on the engine.
Whatever percentage the 9.1 is, is what should be factored in calculating the new speed.
2006-11-04 02:41:12 · answer #2 · answered by Not so Fast 2 · 0⤊ 1⤋
find acceleration
Fv= P
(6600/9.81)a(110000)/(60x60) = 57000
a = 2.7727m/s^2
when car moving up hill it experiences gravitationalforce
resolve gravitational force with respect to e inclined slope therefore,
(mgsin9.81)v + mav = P
v( mgsin9.81 + ma) = P
v ( 6600sin9.81 + 6600/9.81 x 2.7727) = 57000
v (1124.517786 + 1865.425) = 57000
v = 19.0639 m/s
v = 68.6km/h
yey =)
2006-11-04 05:23:23 · answer #3 · answered by abc 1 · 0⤊ 1⤋
The third answer is correct.Therefore there is no more answer for U my friend...
End...Thank U...Ramin
2006-11-04 07:43:08 · answer #4 · answered by raminop2002 2 · 0⤊ 0⤋