A thin rod of length 1 m is fixed in a vertical position inside a train, which is moving horizontally with constant acceleration 4 m/s2. A bead can slide on the rod, and friction coefficient between them is 1/2. If the bead is released from rest at the top of the rod, find the time when it will reach at the bottom.

Solution) If mass of bead is m;

mg-µN=ma

 Now, N=pseudo force due to acceleration of train, which is equal to 4m Newton.

 =>   mg-µ(4m)=ma

=>  g-4µ=a

=>  a=8ms-2

 Using, second equation of motion:

1=0.5(8)t2

T=0.5sec