All 20 questions from the Post-UTME Screening (Post-UTME) Physics 2017 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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Which of the following is a consequence of a force field?
A force field (like a gravitational field) exerts a pull on masses within it - gravitational pull is the direct consequence described.
Which of the following is used to determine the relative density of the acid in a car battery (cell)?
A hydrometer measures the density/specific gravity of liquids such as battery acid.
The motion of the prongs of a sounding tuning fork can rightly be described as
A vibrating tuning fork's prongs move back and forth about a fixed position - vibratory motion.
A simple microscope forms an image at the near point. If the focal length of the microscope is such that..., how far is the object from the lens?
Flagged: part of this question's numeric data was not fully legible in the scan; the magnifier equation 1/v - 1/u = 1/f was used with the given near-point distance to estimate the closest matching option.
An avocado fruit drops from a tree 45m tall. How long does it take to reach the ground?
Using h = (1/2)gt^2 with g=10ms^-2: 45 = 5t^2 => t^2=9 => t=3.0s.
Which of the following is a scalar quantity?
Distance has magnitude only, with no direction, making it a scalar quantity (unlike displacement, acceleration or momentum).
A ball bearing is gently released from rest and allowed to fall through a viscous fluid. Which statement about its motion is correct?
As the ball accelerates, viscous drag increases until it balances weight; at that point acceleration becomes zero and velocity is constant (terminal velocity).
When the vapour of a substance is in equilibrium with its own liquid, it is said to be
A vapour in equilibrium with its liquid phase (no net evaporation or condensation) is described as saturated.
A man standing between two parallel mirrors in a barber's shop will see the following number of his own image
Parallel mirrors facing each other produce a theoretically infinite series of repeated reflections.
If the wavelength of a wave travelling with a velocity of 360ms^-1 is 60cm, the period of the wave is
T = wavelength/velocity = 0.6m/360m/s = 0.00167s. Flagged: this does not cleanly match any listed option; the closest is marked with reduced confidence.
An object is placed at a distance of 20cm in front of a concave mirror. If the magnification is I (unity), what is the focal length of the mirror?
For unit magnification with a real, inverted image, the object is at the centre of curvature (u=2f=20cm), giving f=10cm.
An object at the bottom of a sheet of glass of thickness 6.6mm appears to be displaced by 2.1mm when viewed from above. What is the refractive index of the glass?
Apparent displacement = t(1-1/n). 2.1 = 6.6(1-1/n). Solving gives n approximately 1.47.
Which of the following is NOT true of total internal reflection?
Total internal reflection only occurs when the angle of incidence exceeds the critical angle, not at all angles of incidence, making this statement false.
The image formed on the retina of a normal eye is
The eye's lens forms a real, inverted image on the retina, which the brain then interprets as upright.
Which of the following electromagnetic radiations has the longest wavelength?
Radio waves have by far the longest wavelength in the electromagnetic spectrum among those listed.
The force between two equal point charges of magnitude 2.0uC is equal to 0.4N. Calculate the distance between the charges.
F = kq1q2/r^2. 0.4 = 9x10^9 x (2x10^-6)^2/r^2. r^2 = 0.036/0.4 = 0.09, so r = 0.3m = 30cm.
Use the diagram above (three capacitors C1, C2 and C3 in series with a 24V battery) to answer this question. In the diagram, three capacitors C1, C2 and C3 are connected in series to a 24V battery. If the capacitances are respectively equal to 2F, 3F and 6F, calculate the potential difference across the capacitor labelled C2.
Series capacitance: 1/C=1/2+1/3+1/6=1, so C=1F. Charge Q=CV=1x24=24C. V2=Q/C2=24/3=8V.
The angle of dip is equal to
The angle of dip is 90 degrees at the magnetic poles (where the field is vertical) and 0 degrees at the magnetic equator.
Use the diagram above (a magnetic field pattern between two poles, with points labelled m, n, p, t) to answer this question. In the diagram above, neutral points occur at
Based on the symmetry of the field pattern shown, the neutral points (where the resultant field is zero) occur at m and p.
A step-down transformer is connected to a mains of 240V. If the secondary coil is 10 000 turns, what is the number of turns in the primary coil when the output voltage is 24V?
Np/Ns = Vp/Vs. Np = Ns x Vp/Vs = 10000 x 240/24 = 100000.
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