Question

A railway coach of mass 10 tonnes moves with a speed of 15 m/sec & stkires the stationery coach of mass 5 tonnes . After collision the carriages move together . What is their common speed & in Wch direction will they move

Answer 1

Given

A railway coach of mass 10 tonnes moves with a speed of 15 m/sec & strikes the stationery coach of mass 5 tonnes . After collision the carriages move together

To Find

Common speed

Concept Used

We need to apply conservation of momentum .

$\bf \pink{\bigstar\ \; m_1u_1+m_2u_2=(m_1+m_2)v}$

where ,

• m denotes mass
• u denotes initial speed
• v denotes common speed of the system

Solution

Given ,

• m₁ = 10 tonnes = 10000 kg
• u₁ = 15 m/s
• m₂ = 5000 kg
• u₁ = 0 m/s

In rest

Apply formula ,

$\bf \green{\bigstar\ \; m_1u_1+m_2u_2=(m_1+m_2)v}\\\\\to \rm (10000)(15)+(5000)(0)=(10000+5000)v\\\\\to \rm 150000=15000v\\\\\to \bf \red{v=10\ m/s\ \; \bigstar}$

So , Common speed of the system is 10 m/s

They both will move in forward direction .

Answer 2

Given :-

• m₁ = 10 tonnes = 10000 kg
• u₁ = 15 m/s
• m₂ = 5000 kg
• u₂ = 0 m/s

To Find :-

• Common Speed between them and in which direction it will move.

Solution :-

We will apply the formula for Conservation Of Momentum.

m₁u₁ + m₂u₂ = m₁ = m₁v₁ + m₂v₂

➭10000 × 15 + 5000 × 0 = (10000 + 5000)v.

➭150000 = 15000v.

➭15000v = 150000.

➭v = 150000/15000.

➭v = 10.

Hence, Common Speed = 10m/s.

And,

They Both will move in forward direction.