- #1
qazxsw11111
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Hi. Let's say I have a lift with a man in it. The lift is moving upwards, and the forces acting on the man if I am not wrong is R (Normal reaction force by floor on man) and weight (mg). Hence R-mg=ma. Correct me if I am wrong or anything.
But my teacher says that (this is a marking point for my mid-year exam),
From Newton’s third law,
When a man is standing in a descending lift (there could be deceleration, acceleration or constant speed i.e. zero acceleration) the magnitude of the force exerted on the man’s feet by the floor is always equal to the magnitude of the force exerted on the lift floor by his feet.
Does this mean that force exerted by man's feet is not the weight of man? I am so confused. My free-body diagram is starting to screw up if I can't even identify the forces
But my teacher says that (this is a marking point for my mid-year exam),
From Newton’s third law,
When a man is standing in a descending lift (there could be deceleration, acceleration or constant speed i.e. zero acceleration) the magnitude of the force exerted on the man’s feet by the floor is always equal to the magnitude of the force exerted on the lift floor by his feet.
Does this mean that force exerted by man's feet is not the weight of man? I am so confused. My free-body diagram is starting to screw up if I can't even identify the forces