Question

Helen is driving her car if the kinetic energy of the car is 8.10 E4 J and the mass of the car and its contents is 1010 kg Helen is driving at a speed of
1.26 m/s
9.01 m/s
12.0m/s
12.6m/s
81.1m/s

Answer 1

( 8.10) x 10^4 J = ½(1010kg)V² 
......................= 505V² 
( 8.10) x 10^4 J =[(.0505) x 10^4] V² ........<==10^4 cancels 
8.10 = .0505 V² 
.........______ 
V = ²√ 160.4 

V= 12.6 m/s 

(that's 12.6m/sec(1km/1000m)(3600secs/1hr) = 45.36kph) 
 my diagram is wrong, it is just an ordinary car,