2011 Physics NECO Theory Past Questions

Hint

Hint

Hint

M = 0.6kg              V = 20 m/s            g = 10 m/s²

At maximum height ½ mv³ = mgh

:. P.E. at M.H         = ½ mv²

= ½ x 0.6 x 20 x 20

= 120 J

Hint

(a). Work is said to be done whenever a force moves its point of application a distance in the direction of the force

Work = F x S

(b).    M = 80kg

H = 1.3m

W = F x S

But F = m g

:. W = m g h

W = 80 x 10 x 1.3

= 1040 J

Hint

Three phenomena that result from the refraction of light are;
a).  swimming pool appears shallower when we look down into it than it actually is.
b).  a partially immersed stick dipped at an angle into water appears bent at the interface between the air and the water. If standing upright, it appears shorter
c).  a coin in a bowl, invisible to the observer becomes visible when water is poured into a bowl.

Hint

(a).

(b).

Hint

(a).

(b).

Hint

There are two laws of electromagnetism

(1). Faraday’s law           (2). Lenz’s law

Faraday’s law states that whenever there is a change in the magnetic lines of force  (e.m.f) is induced, the strength of which is proportional to the rate of change of the flux linked with the circuit.

Lenz’s law states that the induced e.m.f is in such direction as to oppose the motion or change producing it.

Hint

Nuclear Fission: This is the breaking up of heavy nucleus into to nuclei of comparable masses when bombarded with fast neutrons or energetic particles releasing energy in the process.

(b). Disadvantages of fusion over fission are

(i).     Fusion is more easily achieve with lightest elements such as hydrogen

(ii).    Law materials required for fusion are more cheaply and readily available

Fusion process produces less dangerous (i.e non radioactive) by-products.

Hint

a.   Types of x-rays

Soft x-rays and hard x-rays

b.

Hint

a. Friction is defined as a force that acts as the surface of separation between two objects in contact and tends to oppose the motion of one over the other.

(i).                                 Advantages of Friction
1). Without friction, it would be impossible to walk or stop walking after getting started.
2). Friction enables the automobile tyres to make a firm grip with the roadway.
3). Friction is utilized in fan belts used over wheels or pulleys in machineries.
4). Friction enables the brakes to stop the car
5). Friction is used in the grinding stone to sharpen knives and chisels.

   Disadvantages of Friction
1). Friction leads too much wear and tear on the moving parts of the machines.
2). Frictions causes loss of energy in the machines, thereby reduces their efficiency.
3). It causes the heating of engines

(ii).                                 Methods of reducing friction

1).     The use of lubricants like oil, grease, air and graphite.

2).     The use of ball or roller bearing

3).     The streamlining of body shapes of moving objects

Hint

                                  The working principle of refrigerator

The working principle of the refrigerator utilizes the cooling effect of evaporation. The coiled copper pipes or tubes which surround the freezing chamber contain a volatile liquid such as ammonia or ethylchloride (Freon). As the liquid evaporates, it absorbs the necessary latent heat of vaporization from the surrounding, thereby cooling the inside of the refrigerator and its contents. The vapour produced is pumped away and compressed in a condenser where it condenses to liquid ammonia. The heat released is dissipated and the liquid is recycled through the evaporator coil and the process is repeated, thus setting up continuous circulation of liquid and vapour.

c(ii)

Hint

a(i). Wave motion is a process of transferring a disturbance (in form of kinetic
energy) from one point to another in a medium without any transfer of
particles of the medium.

C(i).   Standing or stationary waves is a wave obtained when two progressive waves of equal amplitude and frequency are traveling in opposite directions and combine together.

C(ii).  A plane progression wave is represented by the equation

Hint

a.  Electrical currents can also be defined as the rate of flow of charge round a circuit.

ii).      Heating effect e.g. electric heater, electric stove, electric kettle, e.t.c.

Chemical effect e.g electroplating

Magnetic effect e.g. relays, electric motor, e.t.c.

b).     Electric field intensity or strength of an electric field E at any point is defined as the force per unit positive charge ( ∑ ) at that point

F  is measured in Newton while q is measured in coulombs

The unit of electric field intensity is N/C

(ii).    Electric line of force are imaginary lines drawn in such a way that the direction at any point (i.e. the direction of the tangent) is the same as the direction of the field at that point.

It is also the path which an isolated small positive charge would follow if placed in the field.

C(i).   Length of the wire

Its cross – sectional area

The nature of the material

C(ii).  Since conductivity

Increase in the length of wire decreases the conductivity of a wire

Increase in the cross-sectional area increases the conductivity of the material

Gold conductors of electricity have larger conductivity than insulators.

Hint

a.  Photo-electric effect is the emission of electrons when radiation of appropriate frequency strikes a metal surface.

b.  A photocell consists of a photo-sensitive surface as a cathode and a wire ring as the anode. If the visible light falls on this surface, electrons are emitted by a process called photo-electric effect and the flow of these electrons can be detected by a micro-ammeter as shown in the diagram. The electrons are usually accelerated from the cathode to the anode which is at a higher potential with the respect to the cathode.

C. Compton effect, photo-electric effect, thermionic emission, emission and absorption of light.

(iii).   I.       mass remaining after 5 mins     =       240 – 42

=       198g

II. time taken for 140g to decay           =       1.8mins