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A metre rule is pivoted at the 20cm mark and it hangs at the 90cm mark from a spring balance 75g wt. Where is the centre of gravity of the metre rule if it weighs 125g?
Date posted:
March 2, 2019
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Suggest why the rate of heat flow through a pane of glass is greater on a windy day.
Date posted:
February 26, 2019
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An electric kettle with a shiny outer surface would be more efficient than one with a dull outer surface. Explain
Date posted:
February 23, 2019
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How many images would be seen from two mirrors when reflecting surfaces make an angle of 60 degree with each other?
Date posted:
February 23, 2019
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A body weighs 32N in kerosene and 30N in water. If the body weighs 40N in air, find the relative density of kerosene.
Date posted:
February 11, 2019
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A metal block of density 7.8g/cm3 weighs 117N in air. Find the weight of the block when fully immersed in water of density 1.0g/cm3.
Date posted:
February 2, 2019
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A particle revolves at 2Hz in a circle of radius 2m. Calculate its:
a) Linear speed
b) Angular velocity
Date posted:
January 29, 2019
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A screen is placed 80cm from an object. A lens is used to produce on the screen an image with a magnification of 3. What is the distance between the object and the lens? Calculate the focal length of that lens.
Date posted:
January 21, 2019
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A bullet is shot vertically upward and rises for a maximum height of 1000m. What is the initial velocity of the bullet and the total time of flight?
Date posted:
January 14, 2019
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Explain why during anomalous expansion of water, heat transfer is limited to conduction and radiation.
Date posted:
December 30, 2018
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State a reason why it may not be possible to suck a liquid into your mouth using drinking straw on the surface of the moon.
Date posted:
December 10, 2018
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State the reason why the speed of the water at the narrow section of a river is higher than at the wider section.
Date posted:
November 29, 2018
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A radioactive element has an initial count rate of 2,400 counts per minute on a scaler. The count rate falls to 300 units per minute in 30 hours, (a) Calculate the half-life of the element (b) If the initial number of atoms in another sample of the same element is 6.0 × 1020, how many atoms will have decayed in 50 hours?
Date posted:
October 17, 2018
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The initial number of atoms in a sample is 5.12 × 1020. If the half-life of the sample is 3.0 seconds, determine the number of atoms that will have decayed after six seconds.
Date posted:
October 17, 2018
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The half-life of a sample of a radioactive substance is 98 minutes. How long does it take for the activity of the sample to reduce to 1/16th of the original value?
Date posted:
October 17, 2018
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Explain ways of detecting nuclear radiation.
Date posted:
October 17, 2018
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Sodium has a work function of 2.0 e: Calculate
(a) The maximum energy and velocity of the emitted electrons when sodium is Illuminated by a radiation of wavelength 150 nm.
(b) Determine the least frequency of radiation by which electrons are emitted. (Take ‘h’ = 6.626 × 10-34 Js, e = 1.6 × 10-19, c = 3.0 × 108 m/s and mass of electron = 9.1 × 10-31 kg).
Date posted:
October 17, 2018
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The threshold frequency for lithium is 5.5 × 1014 Hz. Calculate the work function for lithium. (Take ‘h’ = 6.626 × 10-34 Js)
Date posted:
October 17, 2018
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Cathode Ray Oscilloscope components and functioning.
Date posted:
October 16, 2018
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Illustrate domestic wiring system with aid of a diagram
Date posted:
October 16, 2018
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A house has five rooms each with a 60 W, 240 V bulb. If the bulbs are switched on from 7.00 pm to 10.30 pm, calculate the;
(a) Power consumed per day in kWh
(b) Cost per week for lighting those rooms if it costs 90 cents per unit.
Date posted:
October 16, 2018
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An electric kettle is rated at 2,500 W and uses a voltage of 240 V. (a) If electricity costs Ksh 1.10 per kWh, what is the cost of running it for 6 hrs? (b) What would be its rate of dissipating energy if the mains voltage was dropped to 120 V?
Date posted:
October 16, 2018
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Explain the process of power transmission
Date posted:
October 16, 2018
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A step-up transformer has 10,000 turns in the secondary coil and 100 turns in the primary coil. An alternating current of 0.5 A flows in the primary circuit when connected to a 12.0 V a.c. supply.
(a) Calculate the voltage across the secondary coil (b) If the transformer has an efficiency of 90%, what is the current in the secondary coil?
Date posted:
October 16, 2018
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A current of 0.6 A is passed through a step up transformer with a primary coil of 200 turns and a current of 0.1 A is obtained in the secondary coil. Determine the number of turns in the secondary coil and the voltage across if the primary coil is connected to a 240 V mains.
Date posted:
October 16, 2018
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A material of density 8.5 gcm-3 is attached to a piece of wood of mass 100g and density 0.2 gcm-3. Calculate the volume of material X which must be attached to the piece of wood so that the two just submerge beneath a liquid of density 1.2 gcm-3.
Date posted:
October 16, 2018
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A balloon made up of a fabric weighing 80 N has a volume of 1.0 × 107 cm. the balloon is filled with hydrogen of density 0.9 kgm-3. Calculate the greatest weight in addition to that of the hydrogen and the fabric, which the balloon can carry in air of average density 1.25 kgm-3
Date posted:
October 16, 2018
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A solid of mass 1.0 kg is suspended using a thread and then submerged in water. If the tension on the thread is 5.0 N, determine the relative density of the solid.
Date posted:
October 16, 2018
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Describe experiment to determine the relative density of a cork
Date posted:
October 16, 2018
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A wooden block of dimensions 3 cm × 3 cm × 4 cm floats vertically in methylated spirit with 4 cm of its length in the spirit. Calculate the weight of the block. (Density of methylated spirit = 8.0 × 102 kgm-3)
Date posted:
October 16, 2018