# Physics 9 Solved Paper 2017 Federal Board

## Class 9 Physics Solved Paper 2017

Class 9 Physics Solved Paper 2017 for Federal Board is available in this post. You can see more FBISE solved past papers of class 9 on our website.

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## Class 9 Physics Solved Paper 2017

### Class 9 Physics Solved Paper 2017Section B

#### Q2.

##### (i) The sun is one hundred and fifty million kilometers away from the earth. Write this:a. As an ordinary whole number b. In scientific notation

Ans: The distance of the Sun from the Earth = 150 million km
a. As an ordinary whole number:
150 million km = 150 x 106km (1 million=106)
150 million km = 150 x 106 x 103m   (1 kilo = 10)
150 million km = 150000000000 m

b. In scientific notation:
150 million km = 150 x 106 x 103
150 million km = 150 x 109
150 million km = 15 x 10 x 109
150 million km = 15 x 1010
150 million km = 1.5 x 1011 m

##### (iii)  Can a body moving at a constant speed have an acceleration?

Ans:   Yes, when a body is moving with constant speed, it can have acceleration if its direction is changing.
For example, if the body is moving along a circle with constant speed, it will have acceleration due to the change of direction at every instant.

##### (v)  Why is it dangerous to travel on the roof of a bus?

Ans.  When a bus suddenly takes a turn, stops, or suddenly speeds up, the passengers on the roof of the bus cannot maintain their balance due to inertia. Therefore, they may fall on either side and may get hurt.

##### (vii)  In a right-angled triangle length of the base is 4 cm and its perpendicular is 3 cm. Find a. Length of hypotenuse b. sinθ    c. cosθ

Sol. Base = 4 cm
Perpendicular = 3 cm
a. Length of Hypotenuse =?
Using Pythagoras Theorem
(Hyp)2 = (Perp)2 + (Base)2
(Hyp)2 = (3)2 + (4)2
(Hyp)2 = 9 + 16
(Hyp)2 = 25
Hyp = 5

b. sinθ=?
Using formula
sinθ = Perp / Hyp
sinθ = 3 / 5

b. cosθ=?
Using formula
cosθ = Base / Hyp
cosθ = 4 / 5

##### (viii)  Differentiate between torque and couple.

Ans. Torque:
The turning effect of a force is called torque or moment of the force. The torque of a force is equal to the product of force and the moment arm of the force.
Couple:
A couple is formed by two parallel forces of the same magnitude but acting in opposite directions along different lines of action.

##### (xi) Why does the value of ‘g’ vary from place to place?

Ans. The value of ‘g’ depends on the distance of a body from the center of the earth. As the earth is not a perfect sphere and its radius is not the same everywhere, therefore, the value of ‘g’ is different at different places.

##### (x)  Which form of energy is most preferred and why?

Ans:  Solar energy is the most preferred form of energy because it is a renewable form of energy. It does not pollute the environment in any way. We can use it, directly and indirectly, every day.

##### (xiii)  Explain how does a submarine move up the water surface and down into the water?

Ans:  Submarines have a system of tanks that can be filled with water and can be emptied from the seawater when required. When the tanks are filled with water, the weight of the submarine becomes greater than upthrust. So, it goes underwater. To let it come up to the surface, the tanks are emptied from seawater.

##### (xiv)  Define latent heat of vaporization.

Ans. Latent Heat of Vaporization:
The quantity of heat that changes the unit mass of a liquid completely into a gas at its boiling point without any change in its temperature is called its latent heat of vaporization.
It is denoted by Hv.
Hv = ΔQv / m
ΔQv = m Hv

##### (xv)  Explain why is double-walled glass vessel used in a thermos flask?

Ans. A vacuum flask consists of three vessels. One is the outer casing which simply holds the inner, double-walled glass vessel which is brightly silvered, both inside and outside. This inside silver lining reflects heat back into the hot liquid inside (or prevents heat from entering into a cold liquid). The outer wall is also silvered on both sides for the same reason. Thus, double-walled glass vessel reduce the transfer of heat due to conduction, convection and radiation.

### Class 9 Physics Solved Paper 2017Section C

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

##### Q3.  b.  Write a note on rolling friction. (04)

Ans.  When a body rolls over a surface, the friction produced is called rolling friction. When a wheel is pushed to move, the force of friction between the wheel and the ground at the point of contact provides the reaction force, which acts opposite to the direction of the applied force. As the body rolls without interlocking of the ups and downs between the two surfaces, therefore the rolling friction is extremely small than the sliding friction. The rolling friction is about 100 times less than sliding friction.

##### Q4.  a. Derive the formula for the speed of the artificial satellite. (05)

Excluded from Syllabus for Annual Exam 2021

##### Q4.  b. Write a detailed note on work. (05)

Sol. WORK
Work is said to be done when a force acts on a body and moves it through some distance in the direction of the force. Work is therefore equal to the product of force and distance. It is given by
Work done = Force x displacement
W = FS

Sometimes the force makes an angle ‘θ’ with the direction of motion, then the work done is given by:
W = (F Cosθ) S
Where F Cosθ is the components of force along which the body moves and covers the distance S.

UNIT OF WORK
The SI unit of work is ‘Joule’. It is defined as the work done when a force of one Newton acts on a body and moves it through a distance of one meter in the direction of the force.

##### Q5.  a. Derive the formula for pressure in any liquid. (04)

Ans. Consider a surface of area A in a liquid at a depth ‘h’ as shown by the shaded region in the figure. The length of the cylinder of liquid over this surface will be h. The force acting on this surface will be the weight w of the liquid above this surface. If ρ is the density of the liquid and m is the mass of liquid above the surface, then
Mass of the liquid cylinder m = volume x density
= (A x h) x ρ
Force acting on area A F = w = mg
F = A h ρ g
As Pressure P = F / A
P = A h ρ g / A
Therefore, Liquid pressure at depth h = P = ρ g h

The above formula gives the pressure at a depth ‘h’ in a liquid of density ρ. It shows that the pressure in a liquid increases with depth.

##### Q5.  b. What is meant by specific heat capacity? Explain. (04)

Ans.  How much heat a body can absorb depends on many factors. Here we define a quantity called heat capacity of a body as “Heat capacity of a body is the quantity of thermal energy absorbed by it for one kelvin (1 K) increase in its temperature”.

Thus, if the temperature of a body increases through DT on adding DQ amount of heat, then its heat capacity will be ∆Q/∆T. Putting the value of DQ, we get
Heat capacity =   ∆Q/∆T =   mc∆T / ∆T
Heat capacity = mc
The above equation shows that the heat capacity of a body is equal to the product of its mass and its specific heat capacity. For example, the heat capacity of 5 kg of water is (5 kg x 4200 Jkg-1K-1= 21000 JK). That is 5kg of water needs 21000 joules of heat for every 1 K rise in its temperature. Thus, the larger is the quantity of a substance, the larger will be its heat capacity.

Sol.