Question

how much does the momentum of the body mass 5kg change when its speed increases from 30-40m/s.

Answer 1

Momentum, p= mv
You can either find momentum in each case and then subtract final from initial to get the change in momentum.
Or,
Change in momentum = m(v1 - v2)
= 5 x (40 - 30) = 50 kgm/s
Hope this helps you.

Answer 2

Momentum = Mass × velocity

For an object of mass m the change in momentum when it’s velocity changes from u to v is
Δp = mv - mu
Δp = m(v - u)

Δp = 5 kg × (40 m/s - 30 m/s)
= 5 kg × 10 m/s
= 50 kg m/s

∴ Momentum of body is increased by 50 kg m/s