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A 300 kg dragster accelerates from the rest to the final speed of 120 m/s in 400 m (about a quarter of a mile) and encounters an average frictional force of 1200 N. What is the average output in watts AND horsepower if this takes 7.30 seconds?

Respuesta :

samuraijack
This problem involves Work and Power

Given: Mass m = 300 Kg;  Initial Velocity Vi = 0;  Final Velocity Vf = 120 m/s

Distance d = 400 m;  Frictional force Ff = 1200 N;  Time t = 7.30 s
 
Frictional Force Ff = 1200 N acting opposite of the Force

Required: Power = ? in unit of watts and Horsepower

Formula:  P = W/t    F = ma   Work = Force x distance or W = fd; a = Vf - Vi/t

                F = ma  F = m(Vf - Vi)/t    F = (300 Kg)(120 m/s - 0 m/s)/7.30 s  

                F = 4, 931.16 N
 
                Force total = Force - Frictional force or Ft = F- Ff

Ft = 4, 931.16 N - 1200 N = 3,731.16 N   
 
P = W/t  =  P = F.d/t   P = (3, 731.16 N)(400 m)/7.3 s   P = 204, 447.12 N m/s or in unit of watts/ convert/ or multiply this number to 0.00134102 Hp

Convert to Horsepower  Hp = 278       






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