A proton in a cyclotron changes its velocity from 30km/sec north to 40km/sec east in  20sec. What is the magnitude of average acceleration during this time?

Given  V1=30 km/S            V2=40 km/S∴ Change in velocity  =V2¯−V1¯                                    =V22+V12−2V1V2cosθ( ∴When direction changes from north to east, θ=90o )                                                  =V22+V12+0=402+302=1600+900=2500=50km/s∴ Average acceleration  a=V2¯−V1¯t                                         =5020=2.5 km/s