I need help with two of these questions.(adsbygoogle = window.adsbygoogle || []).push({});

1. An electron is travelling at 0.866c, with respect to the face of a television picture tube. What is the value of its relativistic momentum to the tube?

Im not goin to post every single step but i'll post my answer.

p=mv/sqrt(1-v^2/c^2)

p=9.11 x 10^-31 x (0.866 x 3.00 x 10^8)/sqrt(0.250044)

p=4.74 x 10^-22

Thats the answer i get but in my book, they have 1.58 x 10^-30.

2. The electron and positron each have a rest mass of 9.11 x 10^-31 kg. In a certain experiment, an electron and positron collide and vanish, leaving only electromagnetic radiation after the interaction. Each particle is moving at a speed of 0.20c relative to the laboratory before the collision. Determine the energy of the electromagnetic radiation.

First of all do i have to solve this question like a collision problem, if i do there is no after situation.

Anyways i think i have to solve for Ek.

So Et=Ek + Erest

Et=mc^2/sqrt(1-v^2/c^2)

Et=9.11 x 10^-31 x (3.00 x 10^8)^2/sqrt(0.96)

Et=8.37 x 10^-14

Erest = 8.2 x 10^-14

Ek= 8.37 x 10^-14 - 8.2 x 10^-14

Ek= 1.7 x 10^-15

But this answer isnt right. In my book they have 0.615 MeV and when i convert my answer to that i dont get that answer. So what did i do wrong ,cant anyone help me please.

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# Relativity problems

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