# 1.A truck weighing 1000kgf changes its speed from 36km/hr to 72 km/hr in 2 mins. calculate: i) the work done by the engine . ii) its power. 2. A body of mass 60kg has the momentum 3000kg m/s. Calculate: i) the kinetic energy. ii) the speed of the body

2
by Deleted account

2015-02-08T01:15:48+05:30
2015-02-09T00:20:41+05:30

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1.
mass of truck = 1000 kg
u = 36 km/h = 10 m/s
v = 72 km/h = 20 m/s
time = 2 min = 2*60 = 120 s
acceleration = (v-u)/t = (20-10)/120 = 1/12 m/s²
force = ma = 1000*(1/12) = 1000/12 N
s=(v²-u²)/2g = (400-100)/2*10 = 15m
Work done = Fs = (1000/12)*15 = 1250 J
Power = W/t = 1250/120 = 104.1 J/s

2.
mass = 60kg
momentum = 3000 kgm/s
KE = p²/2m = 3000²/(2*60) = 75000 J = 75 kJ
velocity = p/m = 3000/60 = 50 m/s