# A car weighing one ton moves at a speed of 72 km / h. How fast a bus weighing 5 tons must move

August 30, 2021 | education

| **A car weighing one ton moves at a speed of 72 km / h. How fast a bus weighing 5 tons must move in order to have the same momentum.**

Vehicle speed:

v1 = 72 km / h = 72000 m / 3600 s = 20 m / s.

Vehicle impulse:

p1 = m1 * v1, where m 1 is the mass of the car.

Bus impulse:

p2 = m2 * v2, where m2 is the mass of the bus, v2 is the speed of the bus.

By condition, the impulses must be equal:

m1 * v1 = m2 * v2;

v2 = (m1 * v1) / m2 = (1000 kg * 20 m / s) / 5000 kg = (20 m / s) / 5 = 4 m / s.

In an hour, the bus will travel: 4 m / s * 3600 s = 14400 m.

Answer: 4 m / s or 14.4 km / h.

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