Question

Proton of mass m collides elastically with a particle of unknown mass at rest. After the collision, the proton and the unknown particle are seen moving at an angle of 90 with respect to each other. The mass of unknown particle is

Answer 1

# Answer- m

# Explaination-

Applying law of conservation of momentum along x-axis

m1u = m1v1.co45 + m2v2.cos45

m1u = 1/√2 (m1v1+m2v2) ...(1)

Applying law of conservation of momentum along y-axis

0 = m1v1.sin45 - m2v2.sin45

0 = 1/√2 (m1v1-m2v2) ...(2)

Coefficient of restitution

e=(v2-v1.cos90)/ucos45

1 = √2.v2/u

u = √2v2 ...(3)

Solving (1)(2)&(3) we get

m1=m2=m

Hence mass of unknown particle will be m.

Answer 2

when both are moving at right angle to each other the mass of unknown particle is also m