A running man has the same kinetic energy as that of a boy of half his mass. The man speeds up by 2m/s and the boy changes his speed by xm/s so that the kinetic energies of the boy and the man are again equal. Then x in m/s is
A
3√2
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
2√2
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
C
√2
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
2
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution
The correct option is B2√2 Let m be mass of the man, vm be speed of the man and m/2 be mass of the boy, vb be speed of the man
Initially, KE of man = KE of boy 12mv2m=12(m2)v2b⇒vb=√2vm
In the second case, 12m(vm+2)2=12(m2)(vb+x)2 ⇒vm+2=1√2[vb+x]=1√2[√2vm+x] ⇒vm+2=vm+x√2 ⇒x√2=2⇒x=2√2
Hence, the correct answer in option (b).