ICSE Class 10 Physics 2019 Question Paper with Solutions

Ans. (i) This claw hammer and nail arrangement belongs to first class of lever. Here, the fulcrum (hammer rests at this point) is closer to the output force than to the input force (force applied by the user).

(ii) Example of class 1 lever where mechanical advantage is greater than one is bottle opener. A small force applied on the bottle opener, exerts a larger force on the cap.

Ans. (b) Given, ratio of masses of bodies \(m_{A}: m_{B}=5: 1\) Ratio of their kinetic energies, \(K_{A}: K_{B}=125: 9\) The formula for kinetic energy \(K=\frac{1}{2} m v^{2}\) Using the formula for bodies A snd B, we get

Dividing \(\mathrm{K}_{\mathrm{A}}\) by \(\mathrm{K}_{\mathrm{B}}\), we get

Now using the data given above, we get

Thus the ratio of velocities \(\mathrm{v}_{\mathrm{A}}: \mathrm{v}_{\mathrm{B}}=5: 3\).

Ans. (i) Heat energy is measured in calories.

(ii) S.I unit of the quality is Joule and the relation between them is

Ans. (i) Couple: Couple is the set of two equal and opposite forces having different line of action. A couple produces rotation without translation. Forces are separated by a distance.

(ii) S.I unit of the moment of couple is Newton meter (Nm).

Ans. (i) Critical Angle: When the angle of incidence of a light ray in a denser medium is such that the angle of refraction becomes 90°, the angle of incidence is called the critical angle. The basic condition for this is to occur light to be incident from denser to rarer medium.

(ii) Important factor which affects the critical angle is the ratio of the refraction indices of the two media.

Ans. (i) Radiation used for photography in fog is infrared radiation.

(ii) Infra-red radiation is a long wavelength and low frequency radiation. Hence, the energy associated with them is also low, so they can penetrate deep into the fog.

Ans. (i)

(ii) Given, refractive index of water, with respect to air \({ }_{\mathrm{a}} \mu_{\mathrm{w}}=\frac{5}{3}\)

∴ refractive index of air with respect to water

Ans. From definition, specific heat capacity of a substance is defined as the amount of heat that raises the temperature of 1 kg substance through 1K. Given specific heat capacity of substance A \(=3800 \mathrm{~J} \mathrm{~kg}^{-1} \mathrm{~K}^{-1}\) and specific heat capacity of substance \(\mathrm{B}=400 \mathrm{~J} \mathrm{~kg}^{-1} \mathrm{~K}^{-1}\). Thus, the amount of heat required to raise the temperature of substance A is much more than that required for substance B. The substance B is a good conductor of heat.

Ans. When a flute is played, the pitch of the note is determined by the length of tube between the mouthpiece and the first open hole. Opening holes to shorten the tube makes the pitch rise, and closing holes to lengthen the tube makes the pitch fall.

Ans. Incidence angle is the angle that incident ray make with the normal to the surface.

Ans. (i) Let \(f_{a}\) be the focal length of lens in air and has the refractive index \({ }_{w} \mu_{g}\). Apply lens maker formula,

Let \(f_{w}\) be the focal length of lens in water when emerged in water where in the refractive index is \({ }_{w} \mu_{g}\)

From equation (i) and (ii)

Since, \(\left({ }_{a} \mu_{g}-1\right)>\left({ }_{w} \mu_{g}-1\right)\) So, \(f_{w}>f_{a}\) Hence , the focal length will be more in water than in air.

(ii) Thin lens has greater focal length.

Ans. (i) The amplitude ratio of two waves

As intensity I:A \({ }^{2}\)

\(\therefore \quad I_{1}: I_{2}=1: 9\)

(ii) Ratio of frequencies \(=1: 1\)

Ans. With the increase in temperature, the specific resistance

(i) of metals increases.

(ii) of semiconductors decreases.

Ans. (i) Each and every object in universe has its natural frequency. If any external object is made to vibrate at the same frequency of the given object then the amplitude of vibration becomes large and the system is said to be in resonance. These are known as resonant vibrations and the frequency is called resonant frequency.

(ii) Frequency makes it possible for us to recognise a person by his voice without seeing him.

Ans. Since, \(\alpha\)-particles has \({ }_{2} \mathrm{He}^{4}\) nuclei. Thus the \(\alpha\)-particles contain two protons and two neutrons. Hence, emission of \(\alpha\)-particle reduces the atomic number by two and atomic weight by four. Thus, \(\left({ }_{1}^{1} \mathrm{H}\right)\) hydrogen nucleus cannot emit an \(\alpha\)-particle

Ans. Equivalent network

Since, \(R_{2}\) and \(R_{3}\) are in series, sot their equivalent resistance \(R_{23}=R_{2}+R_{3}\)

Again \(R_{2,3} \| R_{4}\), so their equivalent resistance \(R^{\prime}\)

or

Finally \(R_{1}\) and \(R^{\prime}\) are in series.

So, their equivalent resistance \(R\) in given as

Ans. (i) Specific heat capacity of a substance changes when its state changes from solid to liquid.

(ii) Specific heat capacity tells you how much energy one must put in per unit mass in order to

raise temperature by 1°C. When you come out of shower you often feel cold. This is because the water on you is evaporating, for this heat flows from your body to the body droplets in order to change their phase from water to gas. You are losing heat and thus feel cold.

Ans. \(x

Ans. (i) In nuclear fusion reaction, the fusion of two light atomic nuclei into a single heavier nuclei by the collision of two interacting particles at extremely high temperatures, with the consequent release of a relatively large amount of energy which defines the thermo nuclear reaction.

(ii) \({ }^{3} \mathrm{He}_{2}+{ }^{2} \mathrm{H}_{1} \rightarrow{ }^{4} \mathrm{He}_{2}+{ }^{1} \mathrm{H}_{1}+\) energy

Ans. Speed of D.C. motor can be increased by

1. varying the flux and by varying the current through field winding.

2. varying supply voltage.

Ans. (i) Total mechanical energy (M.E.) of the body is conserved that is constant throughout to fall the given height.

Since, the mechanical energy is constant at every point. Hence, the mechanical energy at height 2 m will be \((M E)_{\mathrm{B}}=500 \mathrm{~J}\)

(ii) Just before hitting the ground, its kinetic energy will be maximum and potential energy will be zero.

\(\therefore K . E .=500 \mathrm{~J}\). (as whole of its P.E. has been converted into K.E.)

Ans. (i)

The sum of the moments of the masses is always zero about the centre of mass. Let weight of the rode be \(m g f\)

or \(m \times 40=40 \times 25 \Rightarrow m=25 g f\) ∴ mass of rod = 25gf

(ii) If 40gf wt is shifted towards 0 mark

F is shifted towards 0 mark to make the system in equilibrium.

Ans. (i) \(T=\) tension force by which rope affects \(E\) \(T^{\prime}=T^{\prime \prime}=\) tension forces by which rope affects the load W

(ii) Velocity ratio of this pulley system is 2.

(iii) If the load is not moving, in that case \(T=E\).

(iv) If the free end of rope moves by a distance \(x\), Load moves by a distance \(=\frac{\text { Effort arm }}{\text { MA }}=\frac{x}{2}\)

Ans. \(i=\) angle of incidence \(\delta=\) angle of deviation As the angle of incidence is increased, the angle of deviation also increases.

\(\delta_{m}=\) angle of minimum deviation

Ans. (i) This type of image formation takes place due to concave lens. (ii)

Ans. Given, object distance \(\boldsymbol{u}=\mathbf{- 2 4 ~ c m}\) focal length, \(f=8 \mathrm{~cm}\)

(i) Since, \(u>f\), hence nature of image so formed, will be (i) real, (ii) inverted (iii) diminished

(ii) To find image distance \(v=\) ?

Using lens formula,

or \(\frac{1}{v}=\frac{1}{8}-\frac{1}{24}=\frac{3-1}{24}=\frac{2}{24}=\frac{1}{2}\) or \(v=12 \mathrm{~cm}\)

(iii) magnification, \(m=\frac{v}{u}=\frac{12 \mathrm{~cm}}{-24 \mathrm{~cm}}=-0.5\) negative sign indicates, inverted image.

Ans. (i) It is the pitch (or frequency) of sound which makes us listen to base drum distinctly from a distance.

(ii) The base drums have greater amplitude of vibration, so the intensity of sound is high, so it becomes audible at larger distance and its frequency distinguishes it from side drums.

Ans. Frequency of pendulum \(=4\) vibrations per second ∴ Time elapsed in 4 vibration \(=1 \mathrm{~s}\) ∴ Time elapsed after 6 vibrations \(=\frac{1}{4} \times 6=\frac{3}{2} \mathrm{~s}\) This means observer hears the echo after 1.5 s. Given speed of sound \(=340 \mathrm{~m} / \mathrm{s}\). ∴ Distance between cliff and the observer

Ans. (i) Pendulum C executes simple harmonic oscillations.

(ii) Pendulum D will also execute force vibrations in phase with first one.

(iii) When the length of pendulum D is increased the oscillations of D will increase.

(iv) Resonance.

Ans. (i) If one of the devices in parallel combination fuses then the other devices keep working without being affected.

(ii) Characteristics of a fuse wire are:

(1) it should have low melting point,

(2) high conductivity

(3) low resistance

(iii) Earth wire is connected to the metallic body of the appliances in a power circuit.

Ans. (i)

(ii) B is neutral and A is live

Ans. (i) When the key k is open resistance of circuit, \(R=(5+0.5)=5.5 \Omega\)

(ii) Current drawn from the cell when the key k is open is

(iii) When the key k is closed, then \(2 \Omega\) and \(3 \Omega\) will be in series and further their equivalent will be in parallel to \(5 \Omega\) as shown in diagram.

∴ resistance of circuit, \(R^{\prime}=2.5+0 . .5=3.0 \Omega\)

(iv) current drawn from the cell,when key is closed , \(I^{\prime}=\frac{E}{R+r}=\frac{3.3}{3}=1.1 A\)

Ans. (i) Calorimetry is the process of measuring the amount of heat released or absorbed during a chemical reaction.

(ii) Colorimeter is made of copper as it is a good conductor of heat with low specific heat capacity . So small amount of heat is absorbed or liberated during heat exchange.

(iii) Calorimeter is made of thin sheets of copper because it decreases the heat capacity of box, thus ensuring small amount of absorption or release of heat during heat exchange.

Ans.

Ans. Here, we will use principle of calorimetry. Heat lost by initial water, calorimeter is equal to the heat absorbed by ‘the added ice. Thus equations becomes

Ans.

Ans. (i) Nuclear fission : It is a type of nuclear reaction in which a heavy nucleus splits up into two lighter nuclei of comparable size. During this reaction tremendous amount of energy is released.

(ii) \({ }_{92}^{235} \mathrm{U}+{ }_{0}^{1} \mathrm{n} \rightarrow{ }_{56}^{144} \mathrm{Ba}+{ }_{36} \mathrm{Kr}^{89}+3{ }_{0}^{1} \mathrm{n}+\) Energy

In the balanced nuclear reaction atomic number should be equal on left and right side So, \(92(\mathrm{U})+0(\mathrm{n})=x(\mathrm{Ba})+36 \mathrm{Kr}+0(\mathrm{n})\)

Similarly, for mass no.

Ans. (i) In first case when a magnetic needle is kept just below the conductor, when the key is closed the current flows from B to A. So, applying Right Hand Thumb Rule just below the conductor, the direction of magnetic field is towards East. So, needle will deflect towards East.

(ii) The deflection is produced due to magnetic field when current is passed through the wire.

(iii) In second case when a magnetic needle is kept just above the conductor, when the key is closed, the current flows from B to A. So, applying Right Hand Thumb Rule just above the conductor, the direction of magnetic field is towards West. So, needle will deflect towards West.

(iv) The device which works on this principle is magnetic sensor, solenoid etc.