help in physics?

Question

a 2000kg truck has a 100kw engine and is travelling 120 km per hour.
find ;
a.time it would take to travel 2km
b.how much work is done by the engine during this time
c. what the force being exerted on the truck during this time

Answer 1

m = 2000kg = 2E3
v = 120 km/h
engine power P = 100kW =1E5

>a.time it would take to travel 2km
t = s/v = 1min

>b.how much work is done by the engine during this time
Work = F*v = P*t*v = P*s
= 1E5 * 1min * 120km/h
= 1E5 * 2km
= 2E8 J

>c. what the force being exerted on the truck during this time
Work (2E8 J) = F*v
v = 120km/h = 2km/min = 2000m/60s = 33.3m/s
F = 2E8 J/ 33.3m/s
= 6E6 N

Answer 2

Assuming the engine is developin full power,

s.
t = (2 km)(60 min/hr)/(120 km/hr) = 1 min.

b.
100 kw = 100 kJ/s
W = (100kJ/s)(60 s) = 6,000 kJ

c.
F = (6,000,000 N-m)/(2,000 m) = 3,000 N