A block weighing 15N rests on a flat surface and a horizontal force of 3N is exerted on it. Determine the friction force on the block

• A. 0.3N
• B. 0.5N
• C. 3.0N
• D. 5.0N

(a) Explain what is meant by a magnetic field

(b)(i) Describe an experiment to show that a magnetic field exists around a straight wire carrying current

(ii) Draw a labelled diagram showing the pattern and direction of the magnetic field rroduced around the wire. (Neglect the earth's magnetic field).

(c) Sketch the magnetic field due to two straight parallel wires carrying current in the same direction. Indicate the neutral point in the field

(d) Explain, with the aid of a labelled diagram, how a delicate magnetic material could be protected from the earth's magnetic field.

(a)(i) State the principal factor that determines the relative stability of a radioactive nucleus.

(ii) Arrange the following radioactive nucleus in decreasing order of stability. Justify your answer: X,W and Y:

\(^40{X}_20\) \(^920{Y}_36\) and \(^95{Z}_42\)

(b)(i) Explain the term ionization potential.

(ii)

The diagram below illustrates energy levels in the hydrogen atom. E, is the energy of the E\(_0\) ground state.

(i) When an electron makes a transition from level n = 3 to level n = 1, it emits a photon of wavelength 1.02x 10\(^{-7}\)m. Calculate E\(_0\).

(ii) Calculate the ionization potential of the hydrogen atom.

(c)(i) Explain the statement, the work function of sodium is 2.0 eV. (ii) Light of wavelength 160 mm is shone on the surface of a sodium metal of work function 2.0 eV. Determine whether photoelectrons will be emitted. [h = 6.6 x 10\(^{-34}\) Js, e = 3.0 x 10\(^{8}\)m/s, I eV = 1.6 x 10\(^{-19}\) J]

Which of the following about an object performing simple harmonic motion is correct? Its acceleration

• A. is maximum at the extreme ends
• B. is constant and directed towards a fixed point
• C. is zero when it is displayed from the equilibrum position
• D. varies linearly with the displacement from a fixed point and is directed towards the fixed point

The uncertinty in determining the duration during which an electron remains in a particular energy level before returning to the ground state is 2.0 x 10\(^{-9}\)s. Calculate the uncertainty in determining its energy at that level [Take \(\frac{h}{2\pi} = h = 1.054 \times 10^{-34}\) Js]

A concave mirror can be used to produce a parallel beam of light if a lighted bulb is placed

• A. between its focus and the pole
• B. at its focus
• C. at its centre of curvature
• D. between its focus and centre of curvature

A lorry accelerates uniformly in a straight line with acceleration of 4ms^-2 and covers a distance of 250 m in a time interval of 10 s. How far will it travel in the next 10 s?

• A. 650
• B. 900
• C. 800
• D. 250

How much heat is emitted when a body of mass 200g cools from 37^oC to 31^oC? (specific heat capacity of the body = 0.4Jg^-1K^-1)

• A. 4800J
• B. 1200J
• C. 480J
• D. 202J

The displacement d produced in a glass block of thickness t and refractive index n when an object is viewed through it is

• A. t
• B. t (1 + 1/n)
• C. t (1-1/n)
• D. t (1/n - 1)

Radio waves emitted from an antenna are picked up by a radar after reflection from an aircraft in 4 x 10^-3S. How far is the aircraft from the antenna? [c = 3 x 10⁸ms^-1 ]

• A. 6.0 x 10²ms^-1
• B. 1.2 x 10³km
• C. 3.0 x 10³km
• D. 6.0 x 10⁵km