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# Help!Mechanics! watch

1. How to do question 1?
Thank you
2. First two parts...doing third now:

(a) Steady speed therefore P=Fv=40000 W
F = 40000/25 = 1600N

(b) Resolve up the slope: P/v - mgsin(arcsin(1/10))- 1600 = 0
Hence P/25 = 1600 + (9.8*800)/10
P = 59600W

Therefore extra power required = 19600W
3. (i)

F=P/v = 40000/25 = 1600N

(ii)

F(g) = mg sin a = 800*9.81/10 = 784.8N

=> extra power = Fv = 784.8*25 = 19620 W

(iii)

F = 900 + 784.8 = 1684.8

=> a = F/m = 1684.8/800 = 2.106 m/s²

v² = u²+2as => s = 25²/(2*2.106) = 148.4 m
4. Resultant force acting on car down the slope =

mgsin(arcsin(1/10))+900 = (800*9.8)/10 + 900
=1684N

Acceleration up the slope = F/m = -1684/800 = -2.105 m/s^2

V^2 = U^2 + 2as
0 = 25^2 + 2*-2.105*s
s= 148.46 m
5. (Original post by elpaw)
(i)

F=P/v = 40000/25 = 1600N

(ii)

F(g) = mg sin a = 800*9.81/10 = 784.8N

=> extra power = Fv = 784.8*25 = 19620 W

(iii)

F = 900 + 784.8 = 1684.8

=> a = F/m = 1292.4/800 = 2.106 m/s²

v² = u²+2as => s = 25²/(2*2.106) = 70.45m
Calculator error there...
6. (Original post by chrisbphd)
Calculator error there...
yeah, just fixed it.
7. Thank you very much

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