Kinematics of Particles QA 11
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The document discusses a physics problem related to kinematics involving a man on a moving escalator. It outlines three cases of movement: escalator moving, man walking, and both walking together, providing the relationships between time and speed. The correct option for the time taken by the man to walk up the moving escalator is indicated as option (d).
![Physics Helpline
L K Satapathy
Kinematics QA 11
Case-3:
Distance covered = S and time taken = t
(1) , (2) and (3)
Correct option = (d)
,ME EG MG ME EGv u v v v v v u v
( ) . . . (3)SS u v t u v
t
1 2
S S Su v
t t t
1 2
1 2
[ ]
t t
t
t t
Ans
1 2
1 2 1 2
1 1 1 t t
t t t t t
Case-2:
Distance covered = S and time taken = t2
, 0 0ME EG MG ME EGv u v v v v u u
2
2
. . . (2)SS ut u
t
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Kinematics of Particles QA 11
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- 2. Physics Helpline L K Satapathy Kinematics QA 11 Question : A man standing on an escalator takes time to reach the top of a tower when the escalator is in motion and takes time to walk up when the escalator is not moving. Then the time taken by him to walk up the moving escalator is (a) (b) (c) (d)1 2t t 1 2t t 1 2 1 2 t t t t 1 2 1 2 t t t t 1t 2t Answer : S A B Case-1: Only the escalator is moving and the man is not walking. Time taken = t1 Case-2: Only the man is walking on the escalator and the escalator is not moving. Time taken = t 2 Case-3: The man is walking on the escalator and the escalator is also moving. Let time taken = t We are required to find the value of t
- 3. Physics Helpline L K Satapathy Kinematics QA 11 Let the distance AB = S Walking speed of the man = u Speed of the escalator = v Case-1: Distance covered = S and time taken = t1 0 , 0ME EG MG ME EGv v v v v v v v 1 1 . . . (1)SS vt v t We will use the following relative velocity notations : (i) Velocity of Man relative to escalator = v ME (ii) Velocity of Escalator relative to Ground = v EG (iii) Velocity of Man relative to Ground = vMG vME + vEG = vMG
- 4. Physics Helpline L K Satapathy Kinematics QA 11 Case-3: Distance covered = S and time taken = t (1) , (2) and (3) Correct option = (d) ,ME EG MG ME EGv u v v v v v u v ( ) . . . (3)SS u v t u v t 1 2 S S Su v t t t 1 2 1 2 [ ] t t t t t Ans 1 2 1 2 1 2 1 1 1 t t t t t t t Case-2: Distance covered = S and time taken = t2 , 0 0ME EG MG ME EGv u v v v v u u 2 2 . . . (2)SS ut u t
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