One way that scientists measure the mass of an unknown particle is to bounce a f

Question

One way that scientists measure the mass of an unknown particle is to bounce a familiar particle, such as a proton or electron, off the unknown particle in a bubble chamber. The initial and rebound velocities of the familiar particle is measured from photographs of the bubbles it creates as it moves; the information is used to determine the mass of the unknown particle.

(a) If a known particle of mass m and initial speed v0 collides elastically, head-on with a stationary unknown particle and then rebounds with speed v, find the mass of the unknown particle in terms of m, v, and v0.
munknown =

m(v+v0)v0?v Wrong answer

(b) If the known particle is a proton and the unknown particle is a neutron, what will be the recoil speed of the proton and the final speed of the neutron?

0ms

v0

0ms

v0

Explanation / Answer

m = mass of familiar particle

mu = mass of unknown particle

Vo = initial velocity of familiar particle

V' = final velocity of unknown particle

V = final velocity of familiar particle

Using conservation of momentum equation for perfectly elastic collision

m Vo = m (-V) + mu V'

mu V' = m (Vo + V)                   Eq-1

using the equation

relative velocity of separation = relative velocity of approach

V' - (-V) = Vo - 0

V' = Vo - V             Eq-2

mu (Vo - V)= m (Vo + V)    

mu = m (Vo + V)/((Vo - V))

b)

neutron and proton have nearly same mass

so mu = m

mu = m (Vo + V)/((Vo - V))

Vo - V = (Vo + V)

V = 0    speed after rebound

and V' = Vo - V

V' = Vo - 0

V' = Vo

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.