How to solve the problems in Physics.

Many of the students feel Physics as a difficult subject. Because, it involves many calculations,mathematical equations .

To solve the problems in Physics, it is essential to have knowledge of Algebra,Trigonometry,Calculus and integration.

Let me explain few steps to solve problems of physics.When a problem is given to you,
# Read the question as many times you want, until you understand it.

# Try to recollect to which branch of the Physics it belongs i.e does it belong to Kinematics or heat or electricity.

# Note down every physical quantity involved in the question, including that physical quantity which has to be calculated in the question, with their symbols Ex:Time as(t); acceleration as (a);mass as (m) .

# Check whether all the physical quantities involved in the question, are in the same system of units C.G.S or F.P.S or S.I system of unit or not.

# If all the physical quantities are not in the same system of units, then convert them in to any one system i.e into either C.G.S or S.I systems of units.

# write an equation relating all the known physical quantities and the physical quantity which has to be determined in the equation.

# Substitute the values of all the physical quantities and constants in the equation.

# Solve the equation for the unknown physical quantity.

# After getting the result write the proper units.

Let me explain with few examples:
Ex 1) A person of mass 50kg in a lift.Calculate the apparent weight of the person when he moves ( i ) up with acceleration of 3 m/sec² ( ii ) moves down with an acceleration of 4 m/sec² ,( g = 10m/sec² ).

Soln: After going through the problem, we can understand that the physical quantities involved in the problem are a)Mass of the person (m) = 50Kg ; b)acceleration of the lift (a) = 3 m/sec²
c) acceleration due to gravity (g) = 10m/sec² , d) apparent mass of the person ( R ) =?

<sup>Part i) Now assume a formula which is connecting m,a,g and R when the lift is moving up, which is R = m(g + a), as all the given physical quantities are in the same system of units i.e S.I system we can directly substitute values in the above equation.
⇒ R = 50 ( 10 + 3) ;R=50(13) ⇒R = 650 N

ii) When the lift is moving down the formula for apparent weight is R =m(g-a)
⇒R = 50(10 - 4) ; R = 50(6) ⇒R =300N.


Ex 2)A 25Kg block is in motion on a rough horizontal surface.A horizontal force of 75N is required to keep the body moving with constant speed.Find the co-efficient of kinetic friction.(g=10</sup> m/sec² ).

^{Soln: After going through the question,we can understand that the physical quantities in the problem are a) fk =75N m=25Kg g=}10 m/sec² µk =?
^{This is a problem of friction, the formula for co-efficient of kinetic friction} µk ^{= fk/mg =75 /25 × 10
⇒}µk ^{= 75/250 = 0.3}