Question

Four identical blocks each of mass m are placed on
the top of a trolley of mass M as shown in the figure.
When a horizontal force of magnitude F is applied to
the trolley, it experiences an acceleration a.
mmmm
M
Smooth horizontal surface
If one of the blocks picked gently from the trolley
while F is still being applied, the trolley will then
accelerate at (M and m always move together]
M. Am​

Answer 1

Explanation:

according to newton's second law

F=ma

therefore f/m=a

here force(f)remains same

new mass=M+m+m+m=M+3m

new acceleration =f/M+3m_____

Answer 2

Solution is F/3m+M

Explanation: Initial mass of truck and blocks = 4m+M

So, Acc. to Newton's second law of motion F=ma,

So, F/m =a

Now, a = F/4m+M

If one block (ie mass 'm') is removed then NEW MASS will be 3m+M.

So, NEW ACCELERATION will be:

Force / New Mass

: F / 3m+M

Hope it might help you :)