Which of the following statements are true of an insulated charged body carrying positive charge? i. it contains excess positive charges. ii. it creates an electric field. iii. it possesses potential energy. iv. it carries electric current.

• A. i and iv only
• B. i and ii only
• C. i, ii, iii only
• D. i, ii, iii and iv

The diagram below illustrates a beaker of water being heated. It is observed that as the bubbles rise they get bigger in size.The reason for this observation is

• A. water pressure on the bubbles decreases
• B. density of water increases with rise in temperature
• C. volume of water increases with rise in temperature
• D. atmospheric pressure on the bubbles decreases

(a)(i) What is an echo? (ii) State two useful applications of echoes.

(iii) Why are the walls, floors and ceilings of a recording studio heavily padded?

(b)(i) Explain timbre and overtones.

(ii) What is resonance?

(c) As a ship approaches a cliff, its siren is sounded and the echo is heard in the ship after 12 seconds. 2.1 minutes later the siren was sounded again and the echo was heard 8 seconds later. If the speed of sound in air is 340 ms\(^{-1}\), calculate the velocity at which the ship was approaching the cliff.

An electron moves with a speed of 2.00 x 10\(^7\) ms\(^{-1}\) in an orbit in a uniform magnetic field of 1.20 x 10\(^{-3}\) T. Calculate the radius of the orbit. [Mass of an electron = 9.11 x 10\(^{-3}\) kg; charge on an electron = 1.61 x 10\(^{-19}\)C]

Which of the following statements about sound is correct?

• A. when sound travels from air to a denser medium, it is refracted away from the normal at the point of incidence
• B. sound travels faster in air than in water
• C. the wavelength of sound changes when it travels from to water
• D. the frequency of it travels from air to water

What is the frequency of a radio wave of wavelength 150m if the velocity of radio waves in free space is 3 x \(10^8ms^{-1}\)?

• A. 4.5 x \(10^{10}\)Hz
• B. 5x \(10^{9}Hz\)
• C. 4.5 x \(10^{8}Hz\)
• D. 2 x \(10^{6}Hz\)

The diagram below represents the stress-strain graph of a loaded wire. Which of these statements is correct?

• A. At J, the wire becomes plastic
• B. J is the yield point
• C. L is the elastic limit
• D. At K, the wire breaks

What is the amount of heat required to raise the temperature of a 0.02 kg of ice cube from \(-10^oC\) to \(10^oC\) ?

[specific latent heat of fusion of ice = 3.34 x \(10^5\) \(Jkg^-1\), Specific heat capacity of water = 4200 \(Jkg^-1\) \(k^-1\)

Specific heat capacity of ice = 2100 \(Jkg^-1\) \(k^-1\)

• A. 6680 J
• B. 1680 J
• C. 7520 J
• D. 7940 J

A body of mass 20g projected vertically upwards in vacuum returns to the point of projection after 1.2s. [g = 10ms\(^{-2}\)]. Calculate the speed of projection

• A. 1.2ms^-1
• B. 6.0ms^-1
• C. 12.0ms^-1
• D. 0.6ms^-1

Materials that can be stretched and still return to their original forms when the stresses are removed are said be

• A. elastic
• B. elastomer
• C. plastic
• D. thermoplastic