- #1
herbgriffin
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Homework Statement
A car of 2 ton mass traveling at 45 kmph approaches a traffic junction. When the car is 100m before the signal, the driver realizes that the green light is about to turn into red in 6 seconds and hence, he accelerates the car uniformly and crosses just before the light turns red. If the frictional resistance is 0.6 kN/ton, determine the power imparted by the engine at that instant.
Answer: 82.9 kW
Homework Equations
P= W/t ; W=Fd
The Attempt at a Solution
Vi = 45 kmph = 12.5 m/s
V= 100m/6sec =16.67 m/s
and i find the acceleration by the formula of V^2= Vi^2+2ax
and i use the formula of summation of forces horizontal : -Ff + F = ma
Ff= (0.6kN/ton)(2ton) = 1.2kN
and when i find F i substitute it to the formula of power F*100m , but my answer is wrong...please help...