Annual Examination – Set 1 വാർഷിക പരീക്ഷ

The speed of light in a transparent medium is 1.5 × 10⁸ m/s. Its refractive index is (speed of light in vacuum c = 3 × 10⁸ m/s)

A car moves along a straight, level road at a steady speed of 60 km/h. The resultant force on the car is

Pick the odd one out and give the reason:
(i) dust comes out when a hanging carpet is beaten   (ii) passengers fall backwards when a bus starts suddenly   (iii) an athlete cannot stop at once at the finishing line   (iv) a coin on a card falls into the glass when the card is flicked away

A girl of mass 40 kg and her father of mass 80 kg stand 2 m apart. Which statement about the gravitational force between them is correct?

The value of the gravitational constant G was first found by experiment by

A wooden block and an iron block of the same volume are held fully under water. The buoyant force is

A box slides along a rough floor and slowly comes to rest. The work done on the box by the force of friction is . (positive / negative / zero)

A 20 kg box is raised to a platform 2 m high, once by lifting it straight up and once by pushing it up a smooth ramp 5 m long. The work done against gravity (g = 10 m/s²) is

A tuning fork is struck on a rubber pad and its prongs are then held tightly in the hand. What happens?

Pick the odd one out and give the reason: odakkuzhal (flute), bugle, conch (shankhu), violin

The refractive index of a type of glass is 1.6. (a) Find the speed of light in this glass. (Speed of light in vacuum c = 3 × 10⁸ m/s) (b) The refractive index of water is 1.33. In which of the two, this glass or water, does light travel faster?

The velocity–time graphs of three vehicles P, Q and R are shown. (a) Which vehicle moves with uniform velocity? (b) Which one has uniform acceleration? (c) Which one has uniform retardation? (d) What does the area under a velocity–time graph give?

Appu pushes a heavy box towards the east with a force of 120 N. At the same time Binu and Chinnu push it towards the west with forces of 50 N and 40 N (figure). Ignore friction. (a) Find the resultant force on the box and its direction. (b) Are the forces on the box balanced or unbalanced? What happens to the box?

Two lead spheres of masses 100 kg and 200 kg are placed with their centres 0.5 m apart. Find the gravitational force between them. (G = 6.67 × 10⁻¹¹ N m²/kg²)

An object hangs from a spring balance. The balance reads 6 N when the object is in air and 5 N when exactly half of the object is under water. (a) Find the buoyant force on the object when it is half immersed. (b) What will the balance read when the object is fully immersed in water? Give a reason.

State whether the work done by the force named is positive, negative or zero. Give a reason in each case.
(a) the force of gravity on a coconut falling from a tree
(b) the braking force on a moving bicycle
(c) the upward force of a boy’s hand on a school bag he carries while walking along a level corridor
(d) the pull of a crane’s cable on a load it lifts

Four 1.5 V cells are joined in series and connected to a resistor. An ammeter in the circuit reads 0.3 A. (a) What is the emf of this battery? (b) Find the resistance of the resistor. (Take the whole emf to be across the resistor.)

Place your fingers lightly on your throat and speak loudly. (a) What do you feel? Name the part whose vibration produces our voice, and say where it is. (b) Name two other parts that also vibrate when we speak.

The velocity of a car on a straight stretch of the National Highway was noted every 2 seconds:

Time t (s)	0	2	4	6	8	10
Velocity v (m/s)	4	8	12	16	16	16

(a) Draw the velocity–time graph (X-axis: 1 cm = 2 s; Y-axis: 1 cm = 4 m/s). (b) Find the acceleration of the car during the first 6 s. (c) Find the total displacement of the car in the 10 s.

The figure shows Galileo’s experiment. A ball is released from A on one side of a U-shaped channel. The other side is made less and less steep (positions 1, 2 and 3). (a) Up to about what height does the ball rise on the other side? (b) What happens to the distance the ball rolls on the other side as the slope is reduced? (c) In position 3 the ball still stops after some time. Why? What would happen if there were nothing to stop it? (d) What conclusion did Galileo draw about the force needed to keep a body moving? Which law of Newton is based on it?

Two bodies attract each other with a gravitational force F. Complete the table, showing your working.

Case	Mass of first body	Mass of second body	Distance between them	Force
Given	m1	m2	d	F
(a)	2m1	3m2	d	?
(b)	m1	m2	3d	?
(c)	2m1	2m2	4d	?

At Ernakulam railway station, Rahul lifts his 12 kg suitcase straight up from the platform to a height of 1.5 m. Then, holding it at that height, he walks 8 m along the level platform. (g = 10 m/s²) (a) Find the work he does against gravity while lifting the suitcase. (b) Find the work done by the force of gravity on the suitcase during the lift. Is it positive or negative? (c) How much work does he do against gravity while walking the 8 m? Why?

The graph shows how the potential difference V across two resistors A and B changes with the current I through them, at constant temperature. (a) What does the straight line through the origin show? (b) Find the resistances of A and B. (c) A and B are connected in series to a 6 V battery. Find the current in the circuit.

A rubber band is stretched tightly over a pencil box, resting on two pencils, and plucked in the middle (figure). (a) What do you hear and see? What kind of motion does the band have? (b) What conclusion about the production of sound do you get? What are such objects called? (c) A veena works in a similar way. Name its main vibrating part and two associated parts that vibrate.

In the physics lab, Neha places a rectangular glass slab PQRS on a sheet of paper and sends a ray of light AB from a ray box on to its face PS (figure). The speed of light in this glass is 2 × 10⁸ m/s. (a) Find the refractive index of the glass. (c = 3 × 10⁸ m/s) (b) Copy and complete the diagram: show the path of the ray inside the slab and after it comes out, with the normals. (c) At which face does the ray bend away from the normal? Why? (d) How is the ray that comes out related to the ray AB? What is meant by lateral shift? Mark it on your diagram.

An aeroplane at Cochin International Airport starts from rest and accelerates uniformly along the runway. It must reach a velocity of 288 km/h to take off, and it covers 2000 m of the runway before it lifts off. (a) Express the take-off velocity in m/s. (b) Find the acceleration of the aeroplane. (c) How long does it run on the runway before taking off? (d) Find its velocity and the distance it has covered 25 s after starting.

In the school lab, Fathima hangs a brass block from a spring balance. In air the balance reads 3.92 N. She lowers the block completely into an overflow jar filled with water up to its spout, and collects the water that overflows in a beaker (figure). The water collected has a mass of 50 g. (g = 9.8 m/s²; density of water = 1000 kg/m³, i.e. 1 g/cm³) (a) Find the weight of the water collected. (b) Using Archimedes’ principle, find the buoyant force on the block and the reading of the spring balance now. (c) Find the volume of the block and its density. (d) She lowers the block a little deeper, still fully under water and not touching the jar. Will the reading change? Why?

Anu has three 1.5 V cells joined in series, a switch and two identical bulbs L₁ and L₂, each of resistance 9 Ω (take it as constant). She makes circuit (a) with the bulbs in series and circuit (b) with the bulbs in parallel (figure). (a) What is the emf of the battery? (b) For circuit (a), find the effective resistance and the current from the battery. (c) For circuit (b), find the effective resistance, the current from the battery and the current through each bulb. (d) In which circuit do the bulbs glow brighter? If L₁ fuses, what happens to L₂ in each circuit?