Class 9 Physics paper 2025 Federal Board Solution
Class 9 Physics paper 2025 Federal Board Solution. 9th Class Physics Paper 2025 Federal Board
Class 9 Physics paper 2025 Federal Board Solution Section B ( Short Question ) 11 x 3 = 33
Attempt all the questions
Q1:- Differentiate between scalar and vector quantities. Give two examples of each.
Vector:-
A vector is that physical quantity which needs magnitude as well as direction to describe it completely.
Examples:- Displacement, velocity, acceleration, force, momentum and torque are vectors.
Scalar:-
A scalar is that physical quantity which needs magnitude only to describe it completely.
Examples:– Distance, speed, mass, time, temperature and energy are scalar.
Q1:- Compare centre of mass and centre of gravity.
Centre of mass:- Centre of mass of a body is that point where the whole mass of the body is assumed to be concentrated.
Centre of gravity:- Centre of gravity is that point where the total weight of the body appears to be acting.
Q2:- A train travelled a distance of 30 km in 7 minutes and 30 seconds. What is its speed? Convert the speed in km |h.
Distance= s = 30 km
$$=\;30\;\times\;100\;m\\=\;30000\;m$$
Time= t =7 min + 30 sec
$$(\;7\times60\;+30\;)\;sec\\=\;450\;sec$$
Speed= v = ?
$$s=\;vt\;or\;v\;=s/t\\v=\frac{30000m}{450\;sec}\\=\;66.67\;m\;s^{-1}\;$$
$$v=\;66.67\;m\;s^{-1}\;\\=\;\frac{66.67}{1000}\;km\;s^{-1}$$
$$=\;\frac{66.67\times3600}{1000}\;km\;h^{-1}\;\\=\;\frac{240012}{1000}\;km\;s^{-1}$$
$$=\;240.012\;km\;h^{-1}$$
Q3:- What kind of motion does a butterfly have? Briefly describe the kind.
A butterfly has random motion.
Random motion is a type of translatory motion.
If the motion of the body is such that every particle of the body moves in the same direction, motion is called a translatory.
Types of translatory:-
There are three types or translatory motion:
- linear motion
- circular motion
- random motion
Random motion:-
If the body moves along an irregular path, motion is called random motion.
Q3:- Compare magnetic and non-magnetic materials.
Magnetic materials:
Magnetic materials stick to magnets and we can magnetize the magnetic materials.
Non-magnetic materials:
Non-magnetic materials do not stick to magnets and we cannot magnetize them.
Magnetic materials have magnetic domains that can align in one direction but non-magnetic materials do not have magnetic domains.
Magnetic materials can be used in making electromagnets and generators. Non-magnetic materials can be used for making non-magnetic tools.
Examples: Iron and Nickel are magnetic. Wood and glass are non-magnetic.
Q4:- A car has kinetic energy. It velocity is doubled by what factor its kinetic energy would change?
If velocity is doubled, kinetic energy increase by a factor of 4.
$$K.E=\frac1{\;2}\;mv^2\\K.E_1=\;\frac12\;m\;{(\;2v\;)}^2$$
$$=\;\frac12\;m\;(\;4v^2\;)\\=\;4.\frac12\;mv^2$$
$$K.E_1=\;4\;(\frac12\;mv^2\;)\\K.E_1=\;4\;K.E$$
If velocity is doubled kinetic energy become four times greater.
Q4:- An about weights 200 N on earth while 50 N on an unknown planet. Find gravitational field strength on that plane
$$Weigth\;on\;Earth\;=\;W_1\\=\;200\;N$$
$$gravitational\;acceleration\;on\;Earth\;\\=\;g_1=\;10\;m\;s^{-2}$$
$$Mass=\;m\;=?\\W_1\;=\;m\;g_1\\W_1\;=m\;(\;10\;m\;s^{-2\;}\;)\\m\;=\;20\;kg$$
$$gravitational\;field\;strength\\on\;that\;planet\;=g_2\;=?$$
$$wieght\;on\;other\;planet\\=w_2\;=50\;N\\w_2\;=m\;g_2$$
$$50\;N=(\;20\;kg\;)\;g_2\\g_2\;=\;\frac{50\;N}{20\;kg}\;\\=\;2.5\;m\;s^{-2}$$
Q5:- Differentiate between contact and non-contact forces.
A contact force is a force that is exerted by one object on the other at the point of contact. For example thrust, air resistance, drag force, normal force, tension force and elastic force.
A non-contact force is a force between two objects which are not in physical contact. For example gravitational force, electrostatic force and magnetic force.
Q5:- Enlist any three applications of Hook’s law.
We use Hook’s law to design springs, to make weighing machines, to make shock absorbers, to make mattresses and cushions and to make watches and clocks.
Hook’s law enables us to determine the elasticity of different materials in laboratories.
Q6:- Show 2000 nano grams in micro grams.
$$1\;nano\;gram\;=\;10^{-9}\;grams\\So\\2000\;nano\;grams=2000\times10^{-9}grams$$
$$2\times10^3\times10^{-9}g=2\times10^{-6}g\\and\;1\;gram\;=\;10^6\;micro\;grams$$
$$So\;\\2\times10^{-6}g=2\times10^{-6}\times10^6\;g\\=2\times10^0\;g=2\times1\;g=\;2\;g\\hence\\2000\;n\;g\;=\;2\;\mu\;g\\$$
Q6:- How pressure of a liquid varies with depth ? Derive a mathematical formula for it.
Pressure of a liquid increases with depth and this difference in pressure between top and bottom surfaces of an object in a fluid causes buoyancy.
Archimedes principle states that, ” A body wholly or partially immersed in a liquid experiences an upward force equal to the weight of the fluid displaced.
$$density\;of\;liquid\;=\;\rho\\Depth\;from\;the\;surface\;=\;h\\Gravitational\;accelegration\;=\;g\\Liquid\;Pressure\;=\;P\\\\$$
We know that W = mg and density is equal to mass divided by volume. we know also say that mass is equal to density times volume.
So after putting the value of mass in the equation W = m g we get
$$W=\;\rho\;V\;g\\But\\V=\;Ah\\So\;\\W\;=\;\rho\;(\;A\;h\;)\;g\\\\$$
Pressure is equal to force per unit area.
$$P=\;\frac WA\\P\;=\;\frac{\;\rho\;(\;A\;h\;)\;g}A\\P\;=\;\;\rho\;g\;h\\\\$$
Q7:- Briefly explain system of gun and bullet using law of conservation of momentum.
When a gun is fired, the bullet moves forward and the gun recoils back due to law of conservation of momentum. Law of conservation of momentum states that for an isolated system, total momentum of the system remains constant.
Before firing both gun and bullet are at rest. Hence velocity of gun and bullet will be zero so their momentum will be zero. Due to law of conservation of momentum, momentum after the firing must also be zero. So forward momentum of the bullet must be equal and opposite to the backward momentum of the gun.
Q7:- How are hydraulic lifts capable of lifting heavy loads ? Show mathematically.
Hydraulic lifts works on Pascal’s law and Pascal’s law states that pressure applied to an enclosed fluid is transmitted in all directions.
$$Pressure\;applied\;on\;large\;piston=P_1\\Pressure\;applied\;on\;small\;piston=P_2\\Force\;applied\;on\;large\;piston\;=\;F_1\\Force\;applied\;on\;small\;piston\;=\;F_2\\Area\;of\;large\;piston\;=\;A_1\\Area\;of\;small\;piston\;=\;A_2\\According\;to\;Pascal’s\;law\\P_1=P_2\\\frac{F_1}{A_1}\;=\;\frac{F_2}{A_2}\\F_1\;=\;\frac{F_2}{A_2}\;\times\;A_1$$
$$If\;A_1\;>\;A_2\;and\;\;F_1\;>\;F_2\\$$
Then a small force on the small piston can lift a heavy load on the large piston.
Q8:- How powerful is car’s engine if it does
$$3\;\times\;10^7\;joule$$
of work in 1 minute ?
P = W/t
$$P\;=\;\frac{3\times10^7\;joule}{1\;minute}\\P\;=\;\frac{30000000\;joule}{60\;second}\\P\;=\;500000\;Watt$$
$$P\;=\;500\;\times1000\;watt\\=\;500\;Kw$$
$$P\;=\;\frac{500000}{746}\;horse\;power\\P\;=\;670\;hp$$
Q8:- What is impulse ? How is it related with force ? Give equation
Impulse is the product of force and time and Impulse is equal to change in momentum of the body.
Impulse = F x t Impulse = Change in momentum
$$impulse\;=\;\bigtriangleup P\\=\;P_f\;-\;P_i$$
Q9:- A solid cylinder of height 1.25 m and diameter of 2m has a mass 350 kg. Calculate its density.
Height of cylinder = h = 1.25 m
Diameter of cylinder = d = 2m
Radius = d/2 = 2m/2 = 1 m
Mass of cylinder = 350 kg
$$Density\;=\;\rho\;=\;?\\Density\;=\;\frac{mass}{volume}\\\rho\;=\;\frac mV\\Volume\;of\;cylinder\;=V=\;\mathrm\pi\;\mathrm r^2\;\mathrm h\\\mathrm{So}\\\mathrm\rho\;=\;\frac{\mathrm m}{\mathrm\pi\;\mathrm r^2\;\mathrm h}\\$$
After putting the values we get
$$\mathrm\rho\;=\;\frac{\mathrm m}{\mathrm\pi\;\mathrm r^2\;\mathrm h}\\\mathrm\rho\;=\;\frac{(350\;\mathrm{kg})}{(3.14)\;{(1\mathrm m)}^2\;(1.25\mathrm m)}\\=\;\frac{350\;\mathrm{kg}}{3.925\;\mathrm m^3}\;=\;89.17\;\mathrm{kg}\;\mathrm m^{-3}\\$$
Q9:- Briefly describe the working of thermocouple thermometer.
To form a closed circuit when two different metals are joined together and their junctions are kept at different temperatures, an electric current is produced in the circuit. The voltage depends on the difference of temperature between the junctions. Cold junction is kept at a fixed known temperature and hot junction is placed where the temperature is to be measured. The voltage or current produced is measured with a galvanometer and this value is then converted into temperature reading
Q10:- Compare permanent magnet and electromagnet.
Strength of permanent magnet cannot be changed and also cannot be switched on or of. It is made up of hard materials like steel. It is used in motors, toys and speakers.
Electromagnet is made by passing current through a coil. Its magnetism is temporary and exits only when current flows through that material. It can easily be switched on or of. It is used in motors and electric bells.
Q10:- Can direction of velocity and acceleration be in opposite direction ? Explain briefly.
Yes it is possible that velocity an acceleration can be in opposite direction. When brakes are applied on a moving car, velocity will be forward but acceleration will be in opposite direction. When a ball is thrown in vertically upward direction, direction of the velocity of the ball will be upward but due to gravity direction of the acceleration will be in downward direction. In simple harmonic motion it can also be observed that velocity and acceleration will be in opposite direction.
Q11:- Earth completes one revolution around the sun in 365.25 days. Find the orbital speed of earth around the sun if it is 150 million km away from the sun ?
Time = 365.65 days = (365.65) (24) hours
= (8775.6) (60) min = (526536) (60) seconds
= 31592160 seconds
Distance of earth from the sun means radius of the orbit.
So
r = 150 million Km
= 150,000,000 km
= 150,000,000,000 m
S= v t
v = s / t
$$For\;earth\;S=\;2\;\mathrm\pi\;\mathrm r\\\mathrm{So}\\\mathrm v\;=\;\frac{\;2\;\mathrm\pi\;\mathrm r}{\mathrm t}$$
$$\mathrm v\;=\;\frac{2\;(\;3.14\;)\;(\;150\;\mathrm{million}\;\mathrm{km}\;)}{31592160\;\mathrm s}\\\mathrm v\;=\;\frac{(6.28)\;(150,000,000,000\;\mathrm m\;)}{31592160\;\mathrm s}\\\mathrm v\;=2.9\;\times10^4\;\mathrm m\;\mathrm s^{-1}\\$$
Q11:- Is it possible to accelerate an object without speeding up or slowing it down ? Justify
Yes, it is possible to accelerate an object without speeding up or down because acceleration is not only a change in speed but also a change in direction of motion. An object moving in a circular path has acceleration without speeding up or slowing down.
Class 9 Physics paper 2025 Federal Board Solution Section C ( Long questions ) 4 x 5 = 20
Attempt all the questions
Q3:- What is manometer ? Make its diagram. Enlist its four applications.
A manometer is a U-shaped tube filled with liquid (Mercury or cooled water). It is used to measure the pressure of gasses or liquids and to measure gas pressure in laboratories, pressure difference in fluid flow experiments, pressure of gases in pipeline and low pressure of gases. It is also used to compare gas pressure with atmospheric pressure.
Q3:- What is meant by Base Physical Quantities and Derived Physical Quantities ? Give three examples of each with symbol and their SI unit.
The quantities which are independent of the other physical quantities are called base quantities. We cannot define any base quantity in terms of any other quantity.
Derived quantities are the quantities which can be defined with reference to base quantities.
There are seven base physical quantities and hence seven base units. Symbol of meter is m, kilogram is kg, second is s, kelvin is K, ampere is A, candela is cd and mole is mol.
Speed, area and volume are derived quantities and their symbols are v, A and V respectively. SI units of v, A and V are meter per second, square meter and cubic meter respectively.
| Name of Unit | Symbol of Unit |
|---|---|
| Meter | m |
| Kilogram | kg |
| Second | s |
| Kelvin | K |
| Ampere | A |
| Candela | cd |
| Mole | mol |
Q4:- Explain the limitations of Newton’s laws of motion.
Newton’s laws are not valid in all situations. At very high speed Newton’s laws fail. They are applicable on at very slow speed as compared to the speed of light. They are also not applicable for very tiny particles like electron and proton. Newton’s second law will be applicable only when mass in constant. Newton’s laws do not give accurate results in the presence of strong gravitational fields. They are valid only in inertial frame of reference.
Q4:- Briefly discuss any ten fields of Physics.
Heat is the study of temperature and energy. For example heat in engine.
Mechanics is the study of motion. For example motion of any moving body in straight line and curved path of missile.
Optics is the study of behaviour of light. For example reflection, refraction and diffraction.
Sound is the study of sound waves. For example echo and ultrasound.
Plasma Physics is the study of plasma state. For example sun.
Electricity is the study of electric charges, circuits and current. For example energy saver and computers.
Magnetism is the study of magnetic fields. For example MRI machines.
Electromagnetism is the study of relation between electricity and magnetism. For example transformers.
Nuclear Physics is the study of nucleus, nuclear energy and radioactivity. For example X-rays.
Astrophysics is the study of universe. For example planets.
Q5:- Discuss Earth’s magnetic field in context of (a) North and south poles with diagram (b) Bio-magnetism
Earth behaves like a huge bar magnet. Earth has a magnetic field that surrounds it. Due to rotation earth has Geographic poles and due to magnetism earth has magnetic poles.
Magnetic south pole lies near the Geographic south pole and magnetic south pole near the Geographic south pole. A magnetic compass needle always points towards the magnetic north pole of earth.
Many living organisms can sense Earth’s magnetic field and use it for navigation. It is called Bio-magnetism. Birds and fishes use Earth’s magnetic field.
Q5:- A hydraulic lift has 0.003 square meter narrow cylinder area while 0.9 square meter wider cylinder area. How much force must be applied at narrow cylinder if a car weighing 1600 kg is to be lifted ?
$$A_1\;=\;0.003\;m^2\\A_2\;=\;0.9\;m^2\\m\;=\;1600\;kg\\F_2\;=\;m\;g\\=\;(1600kg)\;(10\;m\;s^{-2})\\=\;16000\;N\\F_1\;=\;?$$
For a hydraulic lift, pressure is same in both the directions
$$\frac{F_1\;}{A_1\;}\;=\;\frac{F_2\;}{A_2\;}\\F_1\;=\;A_1\;\;(\frac{F_2\;}{A_2\;})\\F_1=0.003\;m^2\;(\frac{16000\;N}{0.9\;m^2}\;)\\F_1\;=\;53.33\;N\\$$
So 53.33 N force must be applied to lift at the narrow cylinder.
Q6:- What is centripetal force ? Give its formula. How this force is provided in case of motion ? Explain with diagram.
A force which is necessary to keep an object moving in a circular path is called centripetal force.
$$F=\;\frac{m\;v^2}r\\$$
Where F is centripetal force. m is the mass of the object, v is the velocity of the object and r is the radius of the circle in which object in moving.
in case of an object which is tied to a string, tension in the string provides the necessary centripetal force. For an automobile which is moving along a curved path, friction provides the necessary centripetal force. In case of a planet which is moving around another object, gravitational force provides the necessary centripetal force.
Q6:- Explain any two states of matter giving complete information about their practical structures with diagram.
Solids have fixed shape and volume. In solids particles are closely packed in an orderly arrangement and strong molecular forces keep particles fixed in position. Particles can only vibrate about their mean positions.
Liquids have fixed volume but not fixed shape. In liquids particles are close but not in fixed position. In liquids forces between the molecules are close but not in fixed position. Intermolecular forces are weaker than solids and particles can slide over each other. Particles of liquid can move freely in the liquid.
Gases have neither fixed shape nor fixed volume. Particles of gases are far apart from each other. There must be negligible force between the particles of gases. Particles of gases moved freely in all directions. They expand to fill the container.
Check! Some important links below.
