- #1
Izekid
- 40
- 0
Here I have a hard one... A car with the mass 1100kg accelerates from 0km/h to 50km/h in 9,0s. In this time intervall the engine exhausts an power of 57kW. How many procent of the power the engine exhauts is used to increase the moveable energy...
For this I take :
Wres = Fres = Wk
Wk= 1/2 M * v^2
First I take Km/h and transform it to m/s 50km/h = 13,8 m/s
then
550kg *13,8^2 = 104742 J Totalty Cars Moveable power
Then to get Fres I use
S=1/2(v-v0)t
S=13,8/2 * 9 = 62,1m
To get Fres I use Wres = F*S
62,1 * 104742 = 6504478,2J = 6504kJ
57kJ/6504kJ=0,0008 = 0,8 procent
Which Is TOTALY WRONG please help me what shall I do!? It shall be around 21%
For this I take :
Wres = Fres = Wk
Wk= 1/2 M * v^2
First I take Km/h and transform it to m/s 50km/h = 13,8 m/s
then
550kg *13,8^2 = 104742 J Totalty Cars Moveable power
Then to get Fres I use
S=1/2(v-v0)t
S=13,8/2 * 9 = 62,1m
To get Fres I use Wres = F*S
62,1 * 104742 = 6504478,2J = 6504kJ
57kJ/6504kJ=0,0008 = 0,8 procent
Which Is TOTALY WRONG please help me what shall I do!? It shall be around 21%