Question

plz do this sum..............

Answer 1

see solution here please

Answer 2

ke=1/2mv^2
decrement in v= 100-20% ×v
= 80% v
80/100×v
4v/5 =change v
now ke= 1/2 ×m×v^2
=1/2 ×m×4v/5^2
= 1/2×m×16v/25
=8mv/25
precentage of change
=8mv^2/25/mv^2/2 ×100
= 8×2/25×2×100
= 8/25×100
=8×4 =32% ans