Question 5.13 A man of mass 70 kg stands on a weighing scale in a lift which is moving
(a) upwards with a uniform speed of 10 m s–1,
(b) downwards with a uniform acceleration of 5 m s–2,
(c) upwards with a uniform acceleration of 5 m s–2.
What would be the readings on the scale in each case?
(d) What would be the reading if the lift mechanism failed and it hurtled down freely under gravity?
Chapter Laws Of Motion Page 110
Answers
Answered by
205
Given ,
Mass of man = 70 Kg
(A) upward wih uniform acceleration means inertial frame of reference.
So, reading on weighing scale = normal reaction = mg = 700N
(B) body moves downward with uniform acceleration 5 m/s². It means body present in non-intertial frame of reference for applying Newton's law use 'Puedo force' .
Hence, normal reaction = m(g - a)
= 70( 10 - 5)
= 70×5 = 35O N
So, reading on weighing scale = 35Kg
(C) upwards with uniform acceleration 5 m/s²
Hence, Pseudo force act downward . e.g ma (↓)
Normal reaction = mg + ma
= 70( 10 + 5)
= 70×15 = 1050 N
Hence, reading on weighing scale= 105 Kg
Mass of man = 70 Kg
(A) upward wih uniform acceleration means inertial frame of reference.
So, reading on weighing scale = normal reaction = mg = 700N
(B) body moves downward with uniform acceleration 5 m/s². It means body present in non-intertial frame of reference for applying Newton's law use 'Puedo force' .
Hence, normal reaction = m(g - a)
= 70( 10 - 5)
= 70×5 = 35O N
So, reading on weighing scale = 35Kg
(C) upwards with uniform acceleration 5 m/s²
Hence, Pseudo force act downward . e.g ma (↓)
Normal reaction = mg + ma
= 70( 10 + 5)
= 70×15 = 1050 N
Hence, reading on weighing scale= 105 Kg
Answered by
35
Explanation:
Hope you will find my answer helpful
Attachments:
Similar questions