Question

a) State and explain Newton’s second law of motion.

b) A 1000 kg vehicle moving with a speed of 20 m/s is brought to rest in a distance of 50 meters. 

i) Find acceleration 

ii) Calculate the unbalanced force acting on the vehicle

Answer 1

a) According to Newton’s second law of motion, the rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the forces acting on it. 

If a body of mass m is having an initial velocity u, then the initial momentum of the body will be mu. Let F be the force acting on the body for time t with a final velocity v. Then the final momentum is mv. Therefore, the change in momentum is mv = mu and time taken is t. 

b) Mass of the vehicle, m = 1000kg 

Initial velocity, u = 20 m/s 

Final velocity, v = 0 m/s 

Distance covered before stopping, s = 50m

 Therefore, v^₂ – u² = 2as 

a = -4 m/s² 

Unbalanced force = ma = -4000N