A car developing a power of 160hp (horse power ) and keeps a speed 18 m/s?

Question

What is the resistance at that speed? Use that 1hp (horse power) = 746W and 1W = 1J/s. Answer in kN

Any help would be appreciated

Answer 1

♣ take 1s time; the car will produce energy E=P*1s, where

P=160hp= 160*746 J/s;

Also the car will make path x=18m;  

♦ the produced energy E goes for compensating work of resistance; that is

E=F*x, hence force of friction is F =E/x = 160*746/18 =6631N;

Answer 2

Power  =   160 h.p   =   160  x  746  =   119360 Watts.

Use the equation:-

   Power(watts)   =   Force(Newton)   x   velocity (metres/second)

  So      119360   =   F   x   18

    F   =   119360 / 18   =   6631 N.