Question

a ball of mass 100g and another of 120g moves towards each other with speed 6m/s and 5m/s respectively. if they stick to each other after colliding , what would be the velocity of the combined mass after the collision ?

Answer 1

assuming the positive direction on right and negative direction on left.

m = mass of ball going right = 100 g = 0.1 kg

v = velocity of ball going right = 6 m/s

M = mass of ball going left = 120 g = 0.12 kg

V = velocity of ball going left = - 5 m/s

V' = velocity of combination after collision

using conservation of momentum

m v + M V = (m + M) V'

inserting the values

(0.1)(6) + (0.12)(- 5) = (0.1 + 0.12) V'

V' = 0 m/s

hence the combination comes to rest

Answer 2

we know that it is a perfect inelastic collison,the velocity after colliding is

v=m1u1+m2 u2/m1+m2

here m1=100g u1=6m/s

m2=120g u2=-5m/s(since both are moving in opposite direction)

v=100(6)+120(-5)/100+120

=600-600/220

=0