JAMB UTME - Physics - 1984

Which of the following statements is (are) NOT true about the emission of the photoelectrons from metallic surfaces? i. all metallic surfaces emits the same number of photoelectrons in a given light ii. most metallic surfaces emit the same number of photoelectrons in visible and infra-red light iii. a metallic surface emits photoelectrons only if the frequency of the incident light is higher than its own characteristics threshold frequency

The lower and upper fixed points marked on a mecury-in-glass thermometer are 210mm apart. The end of the mercury column in the tube is 49mm above the lower fixed point in a room. What is the temperature of the room in degrees Celsius?

Answer Details

210mm .... 100oC

49mm .... $\theta$

0mm .... 0oC

$\frac{49-0}{210-0}$ = $\frac{\theta -0}{100-0}$

$\frac{49}{210}$ = $\frac{\theta }{100}$

$\theta$ = 23.3oC

What is the cost of running five 50W lamps and four 100W lamps for 10 hours if electrical energy costs 2 kobo per kWh?

Answer Details

PT = (5 x 50) + (100 x 4)

= 650watts

Energy(kWhr) = 650 x 10-3 x 10

= 6.5 kWhr

1kWhr cost 2 kobo ; 6.5 kWhr will cost $\frac{2\times 6.5}{1}$

= 13 kobo

The spectrum of white light consists of coloured lights arranged in the following order

Of two identical tuning forks with natural frequency 256Hz, one is loaded so that 4 beats per second are heard when they are sounded together. What is the frequency of the loaded tuning fork?

Answer Details

Beat = F2 - F1

4 = F2 - 256

F2 = 260Hz

A short bar magnet is placed in earth's magnetic field, as shown above, which of the points II and III are/is possible positions of a neutral point?

A body of mass 5kg initially at rest is acted upon by two mutually perpendicular forces 12N and 5N as shown in fig.3. If the particle moves in the direction QA, calculate the magnitude of the acceleration

Answer Details

R = $\sqrt{{12}^2+5^2}$

R = 13N and R = F = ma

13 = 5 x a

= 2.60ms-2

A force varying linearly with the distance acts on a body as shown above, The work done on the body by the force during the first 10m of motion is

Which of the following statements is (are) NOT correct? i. pressure changes do not affect the speed of sound in air ii. the velocity of sound increases with temperature iii. the quality of the note depends only on its frequency

A plane inclined at an angle of 30o to the horizontal has an efficiency of 60%. The force parallel to the plane required to push a load of 120N uniformly up the plane is

Answer Details

V.R = $\frac{1}{sin30}$ = 2

Efficiency = $\frac{m.A}{V.R}$ x 100%

60 = $\frac{120}{effort}$ x $\frac{1}{2}$ x 100

Effort = 100N

What is the apparent colour of a RED SHIRT when viewed in PURE green light?

Two cells each of e.m.f. 1.5V and an internal resistance 2$?$ are connected in parallel. Calculate the current flowing when the cells are connected to a 1$?$ resistor

Answer Details

E = 1.5v

rT = $\frac{2\times 2}{2+2}$
= 1

e.m.f. = I(R + r)

1.5 = I(1 + 1)

I = 0.75$\Omega$

A particle moves in a circular orbit of radius 0.02m. If the speed of the particle is 0.88ms-1, calculate its frequency in cycles per second

Answer Details

W = $\frac{v}{r}$

= $\frac{0.88}{0.02}$ = 44 rad/s

2$\pi$F = W = 44

F = $\frac{44}{2\times 3.142}$

= 7Hz

A given mass of an ideal gas occupies a volume V at a temperature T and under a pressure p. If the pressure is increased to 2p and the temperature reduced to $\frac{1}{2T}$, then the percentage change in the volume of the gas is

Answer Details

$\frac{P_2{V}_2}{T_2}$ = $\frac{P_1{V}_1}{T_1}$

P2 = 2P1

T1 = 2T2

$\frac{2P_1{V}_2}{T_2}$ = $\frac{P_1{V}_1}{2T_1}$

V2 --V1

% change = $\frac{V_1-\frac{1}{4}{V}_1}{V_1}$ X 100%

= 75%

What volume of alcohol with a density of 8.4 x 102kgm-3 will have the same mass as 4.2m3of petrol whose density is 7.2 x 102kgm-3?

Answer Details

Mass = Density x Volume

4.2 x 7.2 x 102 = v x 8.4 x 102

= 3.6m3

If a solid changes directly into a gas when heat is applied the process is called

Heat is supplied uniformly at the rate of 100W to 1.0 x 10-2kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5oC, then the specific heat capacity of the liquid is

Answer Details

Heat energy = Electrical energy

mc$\theta$ = power x time

5 x 1 x 10-2 x C = 100 x 20

C = 4.0 x 104Jkg-1k-1

Dewpoint is the temperature at which, water vapour in the atmosphere

For a concave mirror to form a teal diminished image, the object must be placed

Which of the following components is NOT contained in a dry cell? A

The resistance of a wire depends on

Cathode rays are

For which of the underlisted quantities is the derived unit ML2T2 correct? i. momentum of a force ii. work iii. acceleration

Answer Details

Moment = force x distance

= m x a x d

= kg x $\frac{m}{s^2}$ x $\frac{m}{1}$

= ML2T2

If a water pump at Kainji Dam is capable of lifting 1000kg of water through a vertical height of 10m in 10s, the power of the pump is [g = 10ms-2]

Answer Details

power = $\frac{\text{work done}}{time}$

= $\frac{1000\times 10\times 10}{10}$

= 10kW

In the circuit Shown above, calculate the effective capacitance between X and Y

A device that converts sound energy into electrical energy is

The unit of quantity of electricity is called

A simple pendulum, 0.6m long, has a period of 1.5s. What is the period of a similar pendulum of 0.4m length in the same location?

Which of the following can be described as high tension transmission?

Which of the following is a correct explanation of the inertia of a body?

All the heat generated in a 5$\Omega$ resistor by 2A flowing for 30 seconds is used to evaporate 5g of a liquid at its boiling point. Which of the following is the correct value of the specific latent heat of the liquid?

Answer Details

Heat energy = electrical energy

mL = I2Rt

5 x L = 2 x 2 x 5 x 30

L = 120Jg-1

Which of the following statements about the compound microscope and astronomical telescope is (are) correct? i. the final image of a compound microscope is located at infinity ii. the final image of the astronomical telescope is always erect iii. the objective lens of a compound microscope has a very short focal length

The distance travelled by a particle starting from rest is plotted against the square of the time elapsed from the commencement of motion. The resulting graph is linear, the slope of this graph is a measure of

For correcting long sight defects in the human eye we require a

When vibration occurs in air column, the distance between a node and an antinode is equal to

The electromotive force obtained from a simple dynamo may be increased by

A coin is placed at the bottom of a cube of glass tern thick. If the refractive index of the glass is $?$, how high does the coin appear to be raised to an observer looking perpendicularly into the glass?

Answer Details

Let apparent depth = X

$\mu$ = $\frac{t}{x}$ $\Rightarrow$ X = $\frac{t}{u}$

raised of coin = t - x

= t - $\frac{t}{\mu }$

= $\frac{t(\mu -I)}{\mu }$

A galvanometer of resistance 5.0W has full-scale deflection for a current of 100mA. How would its range be extended to 1.0A? By placing a resistance of

A gun of mass 2.0kg fires a bullet of mass 16 x 10 -2kg due East. If the bullet leaves the nozzle of the gun with a velocity of 150ms-1, what is the recoil velocity of the gun?

Answer Details

Gun momentum = bullet momentum

2 x v = 1.6 x 10-2 x 150

v = 1.2ms-1 in opposite direction

Which of the following statements describes an atom accurately? i. atoms of all elements are identical ii. an atom contains a nucleus and number of electrons iii. due to the electrons in the atom an atom is negatively charged iv. electrons in the atom move in circular orbits round the nucleus

Which of the following properties of matter CANNOT be utilized for temperature measurement? The

Which of the following i. $\beta$-particles ii. protons iii. neutrons iv. $\alpha$-particles. may be found in light nuclei?

What is the resistance of the circuit shown above

Radio waves have a velocity of 3 x 108ms-1. A radio station sends out a broadcast on a frequency of 800kHz. The wavelength of the broadcast is

Answer Details

v = F$\lambda$

3 x 108 = $\lambda$ x 800 x 103

$\lambda$ = 375.0m

A small steel needle is carefully floated on water in a beaker. When a few drops of kerosine are introduced into the water the needle sink. Which of the following statements correctly explain(s) the observation? i. there is tension on the water surface ii. kerosine reduces the density of water so that needle becomes denser than water iii. kerosine reduces the surface tension of water