Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEET 2019
Exam
NEET
Year
2019
Subject
Physics
Chapter
Motion in One Dimension

NEET 2019 · Physics · Motion in One Dimension

A person standing on the floor of an elevator drops a coin. The...

A person standing on the floor of an elevator drops a coin. The coin reaches the floor in time t1t_1 if the elevator is at rest and in time t2t_2 if the elevator is moving uniformly. The which of the following option is correct?

Options

  1. At1<t2t_1 < t_2 or t1>t2t_1>t_2 depending upon whether the lift is going up or down
  2. Bt1<t2t_1 < t_2
  3. Ct1>t2t_1>t_2
  4. Dt1=t2t_1=t_2

Correct answer

D. t1=t2t_1=t_2

Step-by-step solution

Let hbethe\mathrm{h}be theheight through which the coin is dropped. Then, according to the equation of motion, it is given as h=ut+12gt2⇒t=2hg[∵u=0]⇒t∝1g\begin{aligned}\mathrm{h}=\mathrm{ut}+\frac{1}{2} \mathrm{gt}^2 \Rightarrow \mathrm{t}=\sqrt{\frac{2 \mathrm{ h}}{\mathrm{ g}}} \quad[\because \mathrm{u}=0] \\ \Rightarrow \quad \mathrm{t} \propto \frac{1}{\sqrt{\mathrm{g}}} \end{aligned}Astheelevatorismovinguniformlyi.e.itsvelocityisconstant,sotheaccelerationiszero.As the elevator is moving uniformly i.e. its velocity is constant, so the acceleration is zero.\thereforeRelativeaccelerationoftheliftwhenitiseithermovingupwardordownwardisgivenas,Relative acceleration of the lift when it is either moving upward or downward is given as,\mathrmg^{\prime}=\mathrm{g} \pm a=g\mathrm{a}=\mathrm{g} \pm 0=\mathrm{g}Hence,thetimeforthecointoreachthefloorwillremainssamei.e.Hence, the time for the coin to reach the floor will remains same i.e.t_1=t_2$.
Practice Motion in One Dimension on Quantrex Academy →

More from Motion in One Dimension

A vehicle runs on a straight road of length 'L'. It travels half the distance with speed… MHT CET Medical 2026For uniform acceleration in linear motion which of the following is NOT CORRECT ? MHT CET Medical 2026Two cars, P and Q move toward each other, getting 8\ m closer every second. If they move… MHT CET Medical 2026A block is kept on the floor of an elevator at rest. The elevator starts descending with… MHT CET Medical 2026The acceleration (a ) -time (t ) graph for the body starting from rest is as shown in the… MHT CET Medical 2026A train accelerates from rest at a constant rate 'p' for some time (attains velocity 'v')… MHT CET Medical 2026The following plots show variation of velocity ( v ) with time ( t ), of a ball thrown… NEET 2026Consider a particle moving along a straight line, whose position as a function of time is… NEET 2026 Full Motion in One Dimension list All NEET PYQs