Question

The aeroplane lands at a speed of 80m/s
After landing, the aeroplane takes 28 s to decelerate to a speed of 10m/s
The mean resultant force on the aeroplane as it decelerates is 750 000N
Calculate the mass of the aeroplane in kg

Answer 1

The acceleration of the aeroplane 

$$a=\frac{v_f-v_i}{t}=\frac{10-80}{28}=-2.5\:\rm m/s^2.$$

The Newton's second law states

$$ma=F.$$

Hence, the mass of the aeroplane

$$m=\frac{F}{a}=\frac{750\: 000}{2.5}=300\:000\:\rm kg.$$