# Physics 9 Solved Paper 2016 Federal Board

## Class 9 Physics Solved Paper 2016

Class 9 Physics Solved Paper 2016 for Federal Board is available in this post. You can see more FBISE solved past papers of class 9 on our website.

## Class 9 Physics Solved Paper 2016

### Class 9 Physics Solved Paper 2016Section B

#### Q2.

##### (i) What is meant by Mechanics and Geophysics?

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##### (ii) An object starts from rest. Write down changed equations for the motion of the object.

Ans. For an object that starts from rest vi = 0
Now first equation of motion is
vf = vi + at
Putting vi = 0
vf = 0 + at
vf = at

The second equation of motion is
S= vi t+½ at2
Putting vi = 0
S = (0) t+ ½ at2
S = ½ at2

The third equation of motion is
2aS = vf2 – vi2
Putting vi = 0
2aS = vf2 – (0)2
2aS = vf2

##### (iii) Define centripetal force and also give its formula.

Ans. Centripetal Force
Centripetal force is a force that keeps a body moving in a circle. It always acts perpendicular to the motion of the body. It is denoted by Fc.
Formula:  Fc = mv2 / r

##### (iv) Differentiate between ‘g’ and ‘G’.

Ans. The ‘g’ is the acceleration due to gravity produced in a free-falling body due to the attraction of the earth. Its value is 9.8 ms-2 on the surface of the earth. Whereas ‘G’ is the gravitational constant and its value is 6.67×10-11 Nm2kg-2.

##### (vi) Why is the base of a vehicle made wide?

Ans. The base of a vehicle is made wide so that the vertical line passing through its centre of gravity should not get out of its base during a turn. This is done to avoid over-turning of vehicles during turning.

##### (vii) Briefly describe that law of gravitation is consistent with Newton’s third law of motion.

Ans.  Consider two masses m1 and m2 such that mass m1 attracts m2 towards it with a force F while mass m2 attracts m1 towards it with a force of the same magnitude F but in opposite direction. If the force acting on m1 is considered as action then the force acting on m2 will be the reaction. The action and reaction due to force of gravitation are equal in magnitude but opposite in direction. This is consistent with Newton’s third law of motion which states, to every action there is always an equal but opposite reaction.

##### (viii) Name and define the unit of power.

Sol. Unit OF Power
SI unit of power is ‘watt’. The power of a body is said to be one watt (1 W) if the work done by it is one Joule in 1 second.
Bigger units of power are:
1 kW = 103 W = 1000 W
1 MW = 106 W = 1000,000 W
1 horse power 1 hp = 746 W

##### (ix) State Pascal’s Law.

Ans: Pascal’s Law
This law states that pressure exerted from outside on a liquid is transmitted equally in all directions. This law has some useful applications.
1. Hydraulic press is used to compress raw cotton and cloth into bails.
2. This law is used in Hydraulic brake systems and in other hydraulic machines.
3. This law is also used at the service stations to lift the cars for washing.

##### (x) Calculate the coefficient of linear thermal expansion of aluminum if the value of its coefficient of volume expansion is 7.2 x 10-5 K-1.

Sol. Coefficient of volume expansion of aluminum = β = 7.2 x 10-5 K-1
Coefficient of linear thermal expansion of aluminum = α =?
Since  β = 3 α
or α = β / 3
α = 7.2×10-5 / 3
α = 2.4 × 10-5 K-1

##### (xi) A cup of hot tea becomes cold after sometime. Why?

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##### (xii) Draw a temperature-time graph showing the change of state of ice into water and steam.

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##### (xiii) What is an Atwood machine?

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##### (xiv) Define centre of gravity.

Ans.    Centre of gravity

A point where the whole weight of the body appears to act vertically downward is called centre of gravity of a body. For example, the centre of gravity of a uniform triangular sheet is the point of intersection of its medians.

##### (xv) Define Stress. Also give its formula and unit.

Ans. Stress
Stress is related to force producing a deformation. It is defined as “the force acting on a unit area at the surface of a body is called stress.” Thus,
Stress = Force / Area
In SI, the unit of stress is newton per square metre (Nm-2).

### Class 9 Physics Solved Paper 2016Section C

#### Attempt any TWO questions. All questions carry equal marks.

##### Q3.  a.  State and explain that law of conservation of momentum.   (1+4)

Ans. Law of Conservation of Momentum
Law of Conservation of momentum states that “The momentum of an isolated system of two or more than two interacting bodies remains constant.”

Consider an isolated system of two spheres of masses ‘m1’ and ‘m2’ moving with velocities ‘u1’ and ‘u2’ respectively in the same direction. If u1> u2, the two spheres will collide with each other. Let their velocities become ‘v1’ and ‘v2’ respectively after the collision.
Thus,
Total momentum before collision = m1u1 + m2u2
Total momentum after collision = m1v1 + m2v2
According to the law of conservation of momentum
m1u1 + m2u2 = m1v1 + m2v2

##### Q4.  a.  Define equilibrium and explain the first condition for equilibrium.    (1+3)

Ans. Equilibrium
A body is said to be in equilibrium if no net force acts on it.
Examples:
A book lying on a table or a picture hanging on a wall

First Condition for Equilibrium
According to this condition, a body is said to be in equilibrium if the sum of all the forces acting along any straight line on a body is zero.
Let ‘n’ number of forces F1, F2, F3,.…,Fn are acting on a body such that
F1+F2+F3………….+Fn = 0
or ƩF= 0
or ƩFx = 0 and ƩFy = 0
Then the body is said to satisfy the first condition of equilibrium.

##### Q4.  b.  A man has pulled a cart through 35 m applying a force of 300N. Find the work done by the man.    (3)

Sol.  Force = F = 300 N
Distance = S = 35 m
Work done = W =?
Using formula
W = F x S
W = 300 x 35
W = 10500 J

##### Q4.  c.  Describe Einstein’s Mass-Energy equation.    (3)

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##### Q5.  a.  Describe the scales of temperature. Give Formulas for the conversion of temperature from one scale to the other.  (3+3)

Excluded from Syllabus for Annual Exam 2021