Question

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?

Answer 1

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