List of practice Questions

The autotrophic mode of nutrition requires

Two wires of diameter 0.25 cm, one made of steel and the other made of brass are loaded as shown in Fig. 8.11. The unloaded length of steel wire is 1.5 m and that of brass wire is 1.0 m. Compute the elongations of the steel and the brass wires.

The unloaded length of steel wire

The xylem in plants are responsible for

The kidneys in human beings are a part of the system for

How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line?

Read the following two statements below carefully and state, with reasons, if it is true or false.

(a) The Young’s modulus of rubber is greater than that of steel;

(b) The stretching of a coil is determined by its shear modulus.

The stress-strain graphs for materials A and B are shown in Fig. 8.10.

The stress-strain graphs for materials

The graphs are drawn to the same scale.

(a) Which of the materials has the greater Young’s modulus?

(b) Which of the two is the stronger material?

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

How will you ‘weigh the sun’, that is estimate its mass? The mean orbital radius of the earth around the sun is 1.5×10⁸ km.

A rocket is fired from the earth towards the sun. At what distance from the earth’s centre is the gravitational force on the rocket zero ? Mass of the sun = 2×10³⁰ kg, mass of the earth = 6×10²⁴ kg. Neglect the effect of other planets etc. (orbital radius= 1.5 × 10¹¹ m).

The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to

A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

Find the derivative of the following functions:
(i) sin x cos x
(ii) sec x
(iii) 5sec x+4cos x
(iv) cosec x
(v) 3cot x+5cosec x
(vi) 5sin x-6cos x+7
(vii) 2tan x-7sec x

What is the far point and near point of the human eye with normal vision?

A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 430 Hz source ? Will the same source be in resonance with the pipe if both ends are open? (speed of sound in air is 340 m s^-1).

How is a voltmeter connected in the circuit to measure the potential difference between two points?

A Cylindrical piece of cork of density of base area A and height h floats in a liquid of density \(\rho_l\) .The cork is depressed slightly and then released. Show that the cork oscillates up and down simple harmonically with a period
\(T\) = \(2π\sqrt{\frac{h\rho}{\rho_lg}}\)
Where \(\rho\) is the density of cork. (Ignore damping due to viscosity of the liquid).

Explain the mechanism of the cleaning action of soaps.

Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be –

Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons

Which of the following hydrocarbons undergo addition reactions: C₂H₆ , C₃H₈ , C₃H₆, C₂H₂ and CH₄ .

From a uniform disk of radius R, a circular hole of radius \(\frac{R}{2}\) is cut out. The centre of the hole is at \(\frac{R}{2}\) from the centre of the original disc. Locate the centre of gravity of the resulting flat body.

What change will you observe if you test soap with litmus paper (red and blue)?

Explain the formation of scum when hard water is treated with soap.

Why are carbon and its compounds used as fuels for most applications?