A train is moving with constant acceleration. When the ends of the train pass by a signal their speeds are 30 km/h and 40 km/h respectively. Calculate the speed of the midpoint of train while passing the signal.

Options

A. 35 km/hr
B. `(25)/(sqrt2) km//hr`
C. `25 sqrt2 km//hr`
D. `25 km//hr`

Answer

C

Explanation

Velocity of midpoint is
`v. = sqrt (( u ^(2) + v ^(2))/( 2 )) = sqrt (((30 ) ^(2) + (40 ^(2))^(2))/( 2))`
`therefore v. = sqrt (( 900+ 1600)/(2)) = sqrt ((2500)/(2))`
`therefore v. = (50)/(sqrt2) = 25 sqrt2 (m)/(s)`