Solve this:
Q.23. What will be the value of maximum acceleration of the truck in the forward direction so that the block kept on the back does not topple?
(1) ag/h
(2) hg/a
(3) ag/2h
(4) h/bg

When truck moves forward with acceleration(alpha) the block gets a pseudo force in backward direction which acts at centre of block and this force gives a anticlockwise torque which must be balanced by clockwise torque provided by weight of block.
torque due to pseudo force=torque due to weight of block
taking toppling condition:
m*(alpha)*(h/2)=m*g*(a/2)
alpha=(a*g)/2