A man weighing 700 N moves up in a lift with an acceleration of 5m/s^{2} Find the force exerted by the man on the floor of the lift. If the acceleration of the lift changes to 3 m/s^{2}. find the change in the traction of the lift.

Mass of the man m=700/9.8 = 71.43 kg

Inertia force on the man,  = 71.43 *  5 = 357.1 N

The FBD of the man is shown in Figure 7.7.

Summation of force in y – direction =  R=1057.1N

When the acceleration changes to 3 m/s^{2}

Inertia force on the man will be = 71.43\times 3 = 214.3N

So, the reaction of lift on the = 700 + 214.3 = 914.3 N

Change in reaction = 1057.1 – 914.3 = 142.8 N