Question

A dog (17 kg) is running with a speed of 2.9 m/s. What is the force required to stop the dog? Assume that the force is horizontal, constant, and is applied over a distance of 0.45 m.

Answer 1

Mass of the dog, = 17 kg

Initial velocity of the dog, = 2.9 m/s

Final velocity of the dog,    = 0 m/s

Distance up to which the force is applied, = 0.45 m

Finding the acceleration using Newton's Equation of Motion,

Substituting,     

The -ve sign shows that the velocity of velocity of the decreased as the Force is applied

Finding the Force using Newton's 2nd law of motion,

Substituting,   

The -ve sign shows that the Force is applied is in opposite direction of displacement.