A van of mass `1500kg` travelling at a speed of 15 m/s is stopped in `10 s` Assuming that all the mechanical energy lost appears as thermal energy in the brakes find the average rate of production of thermal energy in cal `s^(-1)`

Answer

A, C, D

Explanation

Mass of van `= 1500kg`
`speed V = 54km//h`
`= 54 xx ((5)/(18)) = 15 m//s`
`Total K.E. = (1)/(2) mv^(2)`
` = (1)/(2)xx 1500xx (15)^(2)`
` = 750xx 225`
= 168750J`
`= 40178cal`
Loss in the tatal energy `= 40175 cal`
In `1` second loss in the total energy
`= (40178)/(10) = 4017.8`
` = 4000 cal//sec`
THe avarage thermal energy cal//sec
`= 4000 cal//sec