Question

7. Two balls, one of mass m and other of mass 2m are moving towards each other with respective speeds of 10 m/s and 20 m/s on a smooth horizontal floor. If after collision they stick to each other and move as combined mass (perfectly inelastic collision), then the speed of combined mass will be [NCERT Pg. 129​

Answer 1

Explanation:

refer the attachment hope its help u

Answer 2

The speed of the combined mass after collision will be 10m/s

Given:

mass of ball 1 (m₁)  = m;

mass of ball 2 (m₂) = 2m;

velocity of ball 1 (v₁) = 10m/s;

velocity of ball 2 (v₂) = -20m/s (negative due to the opposite direction)

To Find:

We need to find the velocity of the combined mass after collision

Solution:

Let the velocity of the combined mass be v

According to law of conservation of momentum,

m₁v₁ + m₂v₂ = (m₁ + m₂)v

On substituting the values of m₁, m₂, v₁ and v₂ we get,

10m + (-20)(2m) = (m + 2m)v

10m - 40m = 3mv

-30m = 3mv

-10m/s = v

v = -10m/s

Therefore the velocity after the collision of two masses is 10m/s in the opposite direction(negative sign).

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