When the lift / elevator is going up, the person experiences an upward acceleration, a.

The resultant force acting on the person is also upward. The equation for the resultant force can be expressed using Newton's Second Law

which is

F = ma

where m = mass of the person.

From the forces (R and W) shown in the diagram above, the resultant force F can also be obtained as such:

R - W = F (resultant force)
R - W = ma
R - mg = ma

R = mg + ma

Hence, the reading of the weighing scale / machine (which is the measurement for R) increases when the lift / elevator is moving upwards with an acceleration.
Putting it another way, it has a reading greater than the actual  weight W = mg of the person.

Click on / Touch the diagram above to continue.

Apabila lif bergerak ke atas, penumpang lif mengalami  pecutan ke atas, a .

Daya paduan yang bertindak pada penumpang juga bertindak ke atas. Persamaan daya paduan boleh dihuraikan menggunakan Hukum Newton Kedua, iaitu

F = ma

di mana m = jisim

Selain daripada itu, menggunakan daya-daya (R dan W) yang ditunjukkan dalam rajah di atas, daya paduan boleh juga diperolehi daripada persamaan berikut

R - W = F
R - W = ma
R - mg = ma

R = mg + ma

Yakni, bacaan skala penimbang (ukuran bagi daya tindak balas R) meingkat apabila lif bergerak ke atas dengan pecutan. Dalam ertikata lain, bacaan penimbang adalah lebih tinggi daripada  berat sebenar penumpang.

Klik / Sentuh pada gambar rajah di atas untuk nota selanjutnya.