Annual Examination – Set 3 വാർഷിക പരീക്ഷ

When light passes from glass into air, the angle of incidence for which the angle of refraction becomes 90° is called the

Pick the odd one out and give the reason:   optical fibre,   mirage,   twinkling of stars,   cycle reflector.

The velocity of a scooter decreases uniformly from 15 m/s to 5 m/s in 5 s. Its retardation is

When a rocket is launched, the upward force on the rocket is exerted by

Find the relation and fill in:   walking : we push the ground backwards  ::  swimming :

An iron block and a copper block have the same mass. Both are fully immersed in water. (Copper is denser than iron.) Which statement is correct?

The readings on the scale of a hydrometer (increase / decrease) from the top to the bottom.

1 watt is equal to

The vibrations of the eardrum are passed on to the

The instrument used to detect hearing loss is the

A lamp O at the bottom of a pond sends two rays OA and OB to the water surface. Ray OA strikes the surface at an angle of incidence of 40° and ray OB at 55° (figure). The critical angle of water is 48.6°. (a) Copy the figure and complete the paths of both rays. (b) Name the phenomenon that happens to ray OB.

A school bus is moving at 36 km/h. The driver sees children at a zebra crossing 25 m ahead and applies the brakes at once. The bus stops in 4 s with uniform retardation. (a) Find the retardation of the bus. (b) Find the distance the bus travels before stopping. Does it stop before the zebra crossing?

Pushing a car from inside, while sitting in it, does not move the car. But when a person standing on the road pushes it, the car moves. Explain why.

A KSRTC bus going round a hairpin bend on the Thamarassery ghat road moves along part of a circular path. (a) Which force provides the centripetal force the bus needs? (b) Why must the driver slow down at such bends?

A lactometer is placed first in whole milk and then in skimmed milk (milk from which the fat has been removed). (a) In which does it sink more? (b) Give the reason.

A lift carries 8 passengers of total mass 560 kg up through a height of 15 m in 20 s. (g = 10 m/s²) (a) Find the work done in lifting the passengers against gravity. (b) Find the power used for this, in watt and in kilowatt.

A uniform wire has a resistance of 4 Ω. It is cut into two equal halves. (a) What is the resistance of each half? (b) The two halves are now joined side by side (in parallel). Find their effective resistance.

Both ends of a plastic bottle are cut off. A piece of balloon is stretched tightly over one end and a few mustard seeds are placed on it (figure). A student speaks loudly into the open end. (a) What happens to the mustard seeds? Why? (b) Which part of our ear works like the balloon diaphragm?

The figure shows an optical fibre with its layers cut back. (a) Name the parts marked 1, 2 and 3. (b) Explain how light reaches the far end of the fibre even when the fibre is bent. (c) Write one use of optical fibres in communication and one in medicine.

A gun of mass 4 kg, free to move, fires a bullet of mass 20 g. The bullet leaves the gun with a velocity of 400 m/s. Both were at rest before firing. (a) Find the momentum of the bullet. (b) Using Newton’s third law, write the momentum the gun gets, with its direction. (c) Find the recoil velocity of the gun.

A stone is dropped from a high bridge into the river 44.1 m below. Ignore air resistance. (g on the Earth = 9.8 m/s², g on the Moon = 1.62 m/s²) (a) How long does it take to reach the water? (b) Find its speed just before it hits the water. (c) How long would the stone take to fall the same height on the Moon?

A metal block of volume 200 cm³ hangs from a spring balance. It is fully immersed in turn in water, kerosene and glycerine (figure). (Density: water 1000 kg/m³, kerosene 810 kg/m³, glycerine 1260 kg/m³; g = 9.8 m/s²; 1 cm³ = 10⁻⁶ m³) (a) Find the buoyant force on the block in water. (b) Find the buoyant force in kerosene and in glycerine. (c) An egg sinks in fresh water but floats in saturated salt solution. Explain using your answers.

A bulb of resistance 6 Ω is connected in series with a rheostat, an ammeter and a 9 V battery (figure). The rheostat wire has 60 turns, each of resistance 0.2 Ω. (a) What is the largest resistance the rheostat can put into the circuit? (b) Find the ammeter reading when all 60 turns are in the circuit. (c) The sliding contact is moved so that only 15 turns are in the circuit. Find the ammeter reading. What happens to the brightness of the bulb?

(a) Classify these as music or noise: a veena recital, a horn blaring at a traffic junction, the drilling at a construction site, chenda melam at a temple festival. (b) Can music become noise? Explain. (c) Loudspeakers are not allowed in public places before 6 am and after 10 pm, and air horns are banned in vehicles. Why are such rules made?

A KSRTC bus leaves a bus stop and stops at the next bus stop on a straight road. Its velocity–time graph is shown. (a) Find its acceleration from O to A. (b) Find its retardation from B to C. (c) Using the area under the graph, find the distance between the two bus stops.

Scientists find a planet X whose mass is 3 times the mass of the Earth and whose radius is 2 times the radius of the Earth. A spacecraft first goes round planet X in a circular orbit and then lands on it. (g on the Earth = 9.8 m/s²) (a) What provides the centripetal force that keeps the spacecraft moving in its circular orbit? (b) Using g = GM/R², find the acceleration due to gravity on planet X. (c) An astronaut of mass 60 kg steps out on planet X. What are her mass and her weight there? (d) She drops a hammer from a height of 14.7 m on planet X. How long does it take to reach the ground?

The figure shows a small hydroelectric power station. Every second, 4000 kg of water flows from the reservoir P down the penstock Q and falls through a height of 50 m to the turbine R, which turns the generator S. (g = 10 m/s²) (a) How much potential energy does the water lose every second? (b) Find the power available from the falling water, in watt and in megawatt. (c) Write the energy change that takes place in the turbine and in the generator. (d) From where did the water in the reservoir get its potential energy?

In the circuit shown, R₁ = 4 Ω is in series with a parallel combination of R₂ = 6 Ω and R₃ = 12 Ω. The battery gives 12 V. (a) Find the effective resistance of the parallel part. (b) Find the total resistance of the circuit and the ammeter reading. (c) Find the current through R₂ and through R₃. (d) R₃ burns out and its wire breaks. What does the ammeter read now? Does the current through R₂ increase or decrease?