Question icon
Grade 11Mechanics

In case of a man standing on weight machine, inside elevator with acceleration upwards,why is g effective = g+a?

Profile image of Aritra De
7 Years agoGrade 11
Answers icon

1 Answer

Profile image of Sneha Harish
ApprovedApproved Tutor Answer7 Years ago
The person seeing this from outside the elevator, is on a stationary frame (inertial frame) and for him, the elevator appears to be accelerating upwards. But for a person inside the elevator (on an accelerating or non inertial frame), the elevator appears to have no upward acceleration because relative to him, the elevator has no accelration. (Like the earth is accelerating but you dont feel it) To express this theoritically, we say a pseudo force or in this case a pseudo (fake) acceleration is acting on the lift in the downward direction. So, according to the person, 2 accelerations are in the downward direction; gravity and the pseudo acceleration. 
Effective acceleration= pseudo acceleration (a) + gravity(g) = a+g
Hence, the effective weight is m(a+g)