Student Swetha's Apparent Weight Experiments in Lift

 11P04 Newton's Laws of Motion

Student Swetha's Apparent Weight Experiments in Lift

(Class 11 student 2023-24)

Actual reading before getting on the lift: 50 kg shown. 
This is approx. 500 N due to gravity alone. Fg = mg = (50) (10) = 500 N.

While the lift is accelerating upwards: 52 kg shown. 
Acceleration will be for few seconds only and then the lift will reach constant velocity.

When the lift is pulled upwards, that is similar to the person getting pushed downwards. So in addition to the gravitational force, the person exerts some more additional force on the weighting machine. Which is seen as the REACTION FORCE R "ON THE PERSON FROM THE WEIGHTING MACHINE".

R - mg = + ma (Acceleration upwards so +ve)

R = mg + ma

R = m (g + a)

520 = 50 (10 + a)

a = + 0.2 m/s2

is the acceleration upwards of the lift.

While the lift is accelerating downwards: 48 kg shown.

Acceleration will be for few seconds only and then the lift will reach constant velocity.

When the lift is going downwards, that is similar to the person getting pushed upwards. So to the gravitational force, the person exerts less force on the weighting machine. Which is seen as the REACTION FORCE R "ON THE PERSON FROM THE WEIGHTING MACHINE".

R - mg = - ma (Acceleration downwards so -ve)

R = mg - ma

R = m (g - a)

480 = 50 (10 - a)

a = - 0.2 m/s2

is the acceleration downwards of the lift.

I wonder why Swetha did not do the last case of cutting the lift rope to experience weightlessness, to show us zero in the scale.