m = 70 kg

10 m/s2 = g

In each scenario, the weighing machine measures the response R, or apparent weight.

(a) The lift’s acceleration equals 0 when it travels upwards at a uniform speed of 10 m/s.

R = mg = 70 x 10 = 700 N

(b) Lift with a = 5 ms-2 going downhill

The equation of motion may be expressed as using Newton’s second law of motion:

Mass of the man, m = 70 kg,

g = 10 m/s2

The weighing machine in each case measures the reaction R, i.e., the apparent weight.

(a) When the lift moves upwards with a uniform speed of 10 m/s, it’s acceleration= 0.

R = mg = 70 x 10 = 700 N

(b) Lift moving downwards with a = 5 ms-2

Using Newton’s second law of motion, the equation of motion can be written as

R+mg = ma

R = m (g – a) = 70 (10 – 5) = 350 N

c) Lift with a = 5 ms-2 going upwards

R = m (g + a) = 70 (10 + 5) = 1050 N

(d) Downward if the lift were to fall freely due to gravity. g = a

R = m(g – g) = m(g – g) = 0

The man will experience weightlessness.