All 12 questions from the Post-UTME Screening (Post-UTME) Physics 2010 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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A machine with a velocity ratio of 6 requires 800J of work to raise a load of 640N through a vertical distance of 1m. Find the efficiency of the machine.
Work output = 640 x 1 = 640J. Efficiency = output/input x100 = 640/800 x100 = 80%.
Which of the following is NOT True about mercury as a thermometric liquid?
Mercury freezes at about -39 degrees C, so it cannot be used for extra-low temperatures down to -200 degrees C - alcohol is used instead for such ranges.
A stone whirled at the end of a rope 35cm long, makes 15 complete revolutions in 4 seconds. Find the angular velocity in radians per second.
Angular velocity = 2*pi*revolutions/time = 2*pi*15/4 = 23.56... actually = (15x2xpi)/4 = 23.6rad/s is closest; recalculating carefully: omega = 2*pi*f = 2*pi*(15/4) = 23.56rad/s, matching option A as the closer value upon recheck.
An object of mass 7kg is moving at a constant velocity of 20ms^-1. Determine the kinetic energy.
KE = 1/2 mv^2 = 0.5 x 7 x 20^2 = 0.5 x 7 x 400 = 1400J = 1.4KJ.
Find the cost of operating an electric appliance for 10 hours at 30 kobo per kwh if it takes 3A when connected to a 220V supply.
Power = VI = 220 x 3 = 660W = 0.66kW. Energy = 0.66 x 10 = 6.6kWh. Cost = 6.6 x 30kobo = 198kobo = N1.98.
Which of the following is not a scalar quantity?
Weight is a force, a vector quantity, unlike density, mass and speed, which are scalars.
Find the resultant of two forces 6N and 5N which are inclined to each other at 30 degrees.
Using the parallelogram law: R = sqrt(6^2+5^2+2x6x5xcos30) = sqrt(36+25+51.96) = sqrt(112.96) = 10.6N.
Which of the following is NOT a property of waves?
A 'ray box' is a piece of apparatus, not a wave property, unlike refraction, polarization and interference.
An object placed 18cm in front of a convex mirror produced an image 6cm behind the mirror. Find the focal length of the mirror.
Using the mirror formula with the sign convention for a convex mirror (image virtual, behind mirror): 1/f = 1/v+1/u = 1/(-6)+1/(-18) = -1/6-1/18 = -3/18-1/18=-4/18=-2/9, giving f=-4.5cm; the closest matching listed value (negative focal length, consistent with a diverging/convex mirror) is option D.
The magnitude of the resultant of two equal vectors, each of magnitude K units and acting at right angle to each other is.....
For two equal perpendicular vectors: R = sqrt(K^2+K^2) = K*sqrt(2).
An orange falls from a height of 20m. How long does it take to reach the ground?
Using h=1/2 g t^2: 20=0.5x10xt^2, t^2=4, t=2.0s.
A piece of stone weighs 80g in air, 50g when completely immersed in water and 65g in liquid Y. What is the relative density of Y?
Upthrust in water = 80-50=30g (equiv to density 1). Upthrust in Y = 80-65=15g. Relative density of Y = 15/30 = 0.5.
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