A 1000kg sports car accelerates from rest to 25.0 m/s in 7.5 s. What is the average power output of the automobile engine?
20.8 kW
30.3 kW
41.7 kW
52.4 kW
i worked this one over and over and i did not get any of these answers so i would appreciate it if someone could share their answers with me.
2006-12-04 14:17:43 · 3 answers · asked by strawberrylollipop12345 1 in Science & Mathematics ➔ Physics
a = 25/7.5 = 3.33 m/s²
F = ma = 1000*a = 3333.333 N (assuming constant acceleration)
d = .5at² = 93.75 m
Energy = F*d = 312500 J
Power = E/t = 41666.667 watts = ~ 41.7 Kw
2006-12-04 14:31:13 · answer #1 · answered by Steve 7 · 0⤊ 0⤋
(Smooth acceleration is assumed because there is not enough information to solve this otherwise).
The average power will be the average energy divided by the timespan.
Energy at start is 0, since the car is at rest. Energy at finish is also ½ times mass times the square of velocity but the values do not include zero so: ½ * 1000 kg * 25 m/s * 25 m/s = 156,250 kg-m^2/s^2. Divide that by the timespan of 7.5 seconds and you get 20,833.3 kg-m^2/s^3. A kW is 1,000 kg-m^2/s^3 so you have 20.8 kW.
Regardless of any... quibbles, I would point out that the problem does not allow any larger answer and the possible answers set includes no smaller answers so I would answer 20.8 kW.
2006-12-04 22:45:08 · answer #2 · answered by roynburton 5 · 0⤊ 0⤋
Pavg=F*Vavg
F=ma
a=(Vf-Vi)/t
Vavg=(Vf+Vi)/2
Vavg=12.5m/s
a=3.33m/s^2
F=3333.33N
Pavg=41666.625w=41.67kw
2014-04-09 00:30:38 · answer #3 · answered by Ruben 1 · 0⤊ 0⤋