Question

Mass of a car is 1000kg.If its speed increase from 36km/hr to 72 km/hr then find gain in its Kinetic energy?

Answer 1

mass=1000 kg

u=36 km/hr=36×5/18=10m/s

v=72 km/hr=72×5/18=20m/s

work done,

W=increase in kinetic energy

=1/2×mv^2-1/2×mu^2

=1/2m(v^2-u^2)

=1/2×1000×(20^2-10^2)

=500×300

=150000 J

87500is the gain in kinetic energy

Answer 2

72 kmph = 72 × 5/18 m/s = 20 m/s
36 kmph = 36 × 5/18 m/s = 10 m/s

Increase in kinetic energy = 0.5 m (v² - u²)
= 0.5 × 1000 kg × [(20 m/s)² - (10 m/s)²]
= 150 × 10³ J
= 150 kJ

Increase in its kinetic energy is 150 kJ