At what temperature will the resistannce of a copper wire become three times its value at `0^(@)C` (Temperature coefficient of resistance for copper `=4xx10^(-3)"per".^(@)C`:-

Options

A. 100 C
B. 200 C
C. 500 C
D. 400 C

Answer

B

Explanation

By applying conservation of momentum
`2(6) + 1(4) = 1v_(2) + 2v_(1), 16 = v_(2) + 2v_(1)` ….(i)
By applying newton law of collision
`1 = (v_(2) - v_(1))/(2) rArr v_(2) - v_(1) = 2` ……(ii)
`rArr v_(2) = (20)/(3), v_(1) (14)/(3)`
To change the direction of a block impulse should be greater than `12 N-s`