Question

A Fireman of mass 80kg slides down a pole during a rescue mission. The force of friction is constant at 720N.Find the acceleration of the man (g=10).

Answer 1

Hint: Friction is the force which bears or resists the relative motion of solid surfaces and sliding against each other. There are different types of frictions and that is dry friction, fluid friction, lubricated friction, skin friction and internal friction. Friction is measured in terms of force and the unit of friction is newton.

Complete step-by-step solution:
There are three newton’s laws of motion and that are newton’s first law, newton’s second law and newton’s third law.
Newton’s first law states that an object at rest continuous to be at rest and an object at motion continuous to be at motion until unless an external force acts on it and velocity of the object is constant when the net force on the body is zero. Newton’s first law is also called the principle of inertia.
Newton’s second law states that the rate of change of momentum of a body with respect to time is directly proportional to the applied force in the same direction as the applied force and inversely proportional to mass.
${{F}_{fm}}=mg-{{f}_{f}}$
$\begin{align}
  & {{F}_{fm}}=80\times 10-720 \\
 & {{F}_{fm}}=800-720 \\
 & {{F}_{fm}}=80N \\
\end{align}$
Newton’s law of motion stated that acceleration of an object is directly proportional to net force and inversely proportional to mass
Force=mass$\times $ acceleration
${{F}_{fm}}=ma$
Substituting the value of ${{F}_{fm}}$ and m in the above equation
$\begin{align}
  & a=\dfrac{{{F}_{fm}}}{m} \\
 & a=\dfrac{80}{80} \\
 & a=1m{{s}^{-2}} \\
\end{align}$
Acceleration of the man $a=1m{{s}^{-2}}$

Note: Students the solution to this problem is obtained by using Newton's law of motion and in this problem value of gravity is given .Acceleration depends on the mass and the force which acts on the body. The force velocity, acceleration and momentum have both magnitude and a direction. Heavier objects have less acceleration compared to lighter objects.