An 18 000-kg freight car travelling 1.75 m/s[E] collides with a 27 000-kg freight car at rest. After the collision, the freight cars stick together. What is the velocity of the freight cars after the collision?

The velocity of the freight cars after collision is 0.7 m/s

Explanation:

Given;

mass of the first freight car, m₁ = 18000 kg

initial speed of the first freight car, u₁ = 1.75 m/s

mass of the second freight car, m₂ = 27000 kg

initial speed of the second freight car, u₂ = 0

Let the velocity of the freight cars after collision = v

Apply the principle of conservation of linear momentum;

m₁u₁ + m₂u₂ = v(m₁ + m₂)

18000(1.75) + 27000(0) = v(18000 + 27000)

31500 = 45000v

v = 31500 / 45000

v = 0.7 m/s

Therefore, the velocity of the freight cars after collision is 0.7 m/s

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j