IIT JEE , AIEEE Forum - Physics , Mechanics

bhartibhanushali

a man in elevator throws a coin with velocity 10m/s upwards
at the same the elevator moves with an accn 4m/s^2
find the time taken by coin to come back to man if
1) lift moves in direction of coin
2) lift moves in opposite direction

please post solution with answer

mukulss

see case 1

in such questions just try 4 relative values:

takin up +ve:

v_rel = +10m/s

a_rel = (+4-10)m/s²

s_rel = 0 (ball has to come back only)

now:

s = ut + gt²/2

0 = 10t - 3t²

t₁ = 10/3sec....

now
case 2:
u_rel = 10m/s(+ve)

a_rel = -10-4 = 14m/s²

s_rel = 0 (same reason)

t₂ = 10/7 sec

saurabh_reincarnated

ya rel. accc.....

applying kinetics

just as mukulsss did

iitkgp_bipin

Use relative acceleration as done by Mukul and then apply 1-D kinematics equations.

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