Question

A free electron is moving with a velocity of 3 × 105 m/s. It strikes a stationary electron in a head-on elastic collision. The mass of an electron is 9.1093 × 10-31 kg. What will be the magnitude and direction of the momentum of the stationary electron, post collision?

Answer 1

273.279 × 10-25 kg.m/s, in the same direction as the incident electron

Step-by-step explanation:

The momentum of the stationary electron post collision will be 273.279 × 10-25 kg.m/s, in the same direction as the incident electron.

Momentum of the incident electron = mv

= 9.1093 × 10-31 × 3 × 105

= 273.279 × 10-25 kg.m/s

In the collision of the electrons, the total momentum is conserved. Since it is an elastic collision, the momentum of the incident electron is completely transferred to the stationary electron. So it will have the same momentum as the incident electron. It will also move in the direction of the incident electron.

Answer 2

After the colision, the stationary electron's momentum is given as:

P = 2.7328 x 10^(-25) kg m/s

The direction of momentum is the same as the direction of velocity of the electron.

Step-by-step explanation:

In an Isolated system, when an object moving at some velocity v collides head on with a stationary object of equal mass. There velocities are exchanged.

This means that the first electron will become stationary and the electron which was stationary initially will start moving at a velocity of 3*10^(5)m/s in the same direction as the first electron.

Post collision momentum of the stationary electron:

V = 3 x 10^5 m/s

m = 9.1093 x 10^(-31) kg

Momentum = P = mV = 9.1093 x 10^(-31) x 3 x 10^5

P = 2.7328 x 10^(-25) kg m/s

The direction of momentum is the same as the velocity of the electron.