Please find the power (in kW) needed in accelerating a 1000 kg car from 0 to 100 km/hour in 10 seconds on a 5% gradient up-hill road.

Respuesta :

Answer:

P= 45.384 kW

Explanation:

given data:

m = 1000 kg

u = 0

v = 100 km/hr = 250/9  m/s

t = 10 sec

g =9.81 m/s2

5% gradient

from figure we can have

[tex]tan\theta = \frac{0.05x}{x}[/tex]

[tex]\theta =  tan^{-1}0.05 [/tex]

[tex]\theta = 2.86[/tex] from equation of motion we have

v = u + at

[tex]\frac{250}{9} = 0 + 9*10[/tex]

[tex]a = \frac{25}{9} m/s^2[/tex]

distance covered  in 10 sec

from equation of motion

[tex]s = ut + \frac{1}{2}at^2[/tex]

[tex]s = 0*10+ \frac{1}{2}*\frac{25}{9}*10^2[/tex]

s = 138.8 m

from newton's 2nd law of motion along inclined position

[tex]F -mgsin\theta  = ma[/tex]

solving for f  

[tex]f = mgsin\theta +ma[/tex]

[tex]F = 1000*9.81*SIN2.8624 +1000*\frac{25}{9}[/tex]

F = 3267.67 N

work done is given as W

[tex]W = F* s[/tex]

and power [tex]P = \frac{W}{t}[/tex]

[tex]P = \frac{F*s}{t}[/tex]

[tex]P = \frac{3267.67*\frac{1250}{9}}{10}[/tex]

P = 45384.30 W

P= 45.384 kW

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