A man of mass 80 kg is in a lift moving upwards. Calculate the normal force exerted by the floor on the man when the lift is moving with a constant velocity of 6 m/s.

15. c)

iv) Moving upwards with a constant velocity of $6 \, \text{m/s}$.

Step 1: Identify the given values.
Mass $m = 80 \, \text{kg}$.
Acceleration $a = 0 \, \text{m/s}^2$ (constant velocity means zero acceleration).
Acceleration due to gravity $g = 9.8 \, \text{m/s}^2$.

Step 2: Apply Newton's second law.
When moving at a constant velocity, the net force is zero. The normal force $N$ exerted by the floor on the man balances the man's weight $mg$.

$$N - mg = ma$$ $$N - mg = m(0)$$ $$$$