Answer:
Explanation: Scale only reads reaction force so we will find out reaction force of ground in different cases.
a ) Let R be the reaction force of floor in the first case.
Net force = R - mg
= mass x acceleration = 0 ( body is at rest ).
R = mg , scale will read his actual weight.
In the case of b) and c) also acceleration is zero hence
R - mg =0
R =mg ,scale will read his actual weight.
d) In this case there is acceleration of 3 m s⁻² in upward direction so
R - mg = ma
R = m( g+a) = 75 x ( 9.8 + 3 ) = 960 N
The reading of scale will be more than his actual weight .
It will read weight as 960/9.8 = 97.96 kg.
e) In this case body is going downwards
mg -R = ma
R = m ( g - a )
= 75 ( 9.8 - 3 )
= 435 N
= 435 / 9.8 kg
= 44.38 kg
So scale will read less than his actual weight.
