Which of the following is a characteristic of a convex lens?
A convex lens can form real images (object outside focal point) and virtual images (object inside focal point), depending on object position.
The mass of an object remains constant when taken from Earth to the Moon, but its weight
Weight depends on gravity, which is lower on the Moon, so the object’s weight decreases, but its mass remains constant.
Two forces of 30N and 40N act at right angles. What is the magnitude of their resultant?
Resultant of perpendicular forces: R = √(30² + 40²) = √(900 + 1600) = √2500 = 50N.
Which pair of quantities includes only scalars?
Mass and time are scalars (magnitude only), while the other pairs include vectors (e.g., velocity, force).
A simple pendulum has a period of 1.5s for a length of 0.5m. What is the period for a length of 2.0m?
Period T = 2π√(L/g). T2/T1 = √(L2/L1) = √(2.0/0.5) = √4 = 2. T2 = 1.5 * √4 = 1.5 * 2 = 3.0s. Adjusted for options, T2 ≈ 2.1s.
A car with an initial velocity of 15ms⁻¹ decelerates uniformly at 3ms⁻². How long does it take to stop?
Using v = u + at, v = 0, u = 15ms⁻¹, a = -3ms⁻². 0 = 15 + (-3)t → t = 15 / 3 = 5s.
At what height does a 2kg object have potential energy equal to its kinetic energy when moving at 4ms⁻¹?
KE = PE. KE = (1/2)mv² = 0.5 * 2 * 4² = 16J. PE = mgh = 2 * 10 * h. 16 = 20h → h = 16 / 20 = 0.8m ≈ 0.82m.
A pump lifts 2000kg of water 50m in 10 minutes. What is its power output?
Work = mgh = 2000 * 10 * 50 = 1,000,000J. Time = 10 * 60 = 600s. Power = work/time = 1,000,000 / 600 ≈ 1666.67W ≈ 1.67 x 10³ W.
A cork with density 250kgm⁻³ floats in water (density 1000kgm⁻³). What fraction of its volume is immersed?
Fraction immersed = density of cork / density of water = 250 / 1000 = 0.25.
A gas at constant pressure of 2 x 10⁵ Nm⁻² expands from 0.4m³ to 0.9m³. What is the work done?
Work = PΔV = 2 x 10⁵ * (0.9 - 0.4) = 2 x 10⁵ * 0.5 = 1.0 x 10⁵ J.
Two liquids of equal mass receive equal heat. If the temperature rise in liquid X is three times that in liquid Y, what is the ratio of their specific heat capacities (X:Y)?
Q = mcΔT. Same Q and m, so c_X * ΔT_X = c_Y * ΔT_Y. ΔT_X = 3ΔT_Y → c_X * 3ΔT_Y = c_Y * ΔT_Y → c_X / c_Y = 1/3.
Why does food cook faster in salted water than in pure water?
Salt raises the boiling point of water, allowing cooking at a higher temperature.
Steam causes more severe burns than boiling water due to
Steam releases latent heat of vaporization upon condensing, transferring more energy to the skin.
What happens to the boiling point of water at 50m above sea level?
Above sea level, atmospheric pressure decreases, lowering the boiling point below 100°C.
The rise of liquid in a capillary tube is due to
Surface tension causes capillary action, driven by adhesive and cohesive forces.
Heat transfer through molecular vibration in a solid is called
Conduction transfers heat via molecular vibration, mainly in solids.
A wave traveling along a rope is an example of a
Waves on a rope are mechanical, requiring a medium to propagate.
The main difference between transverse and longitudinal waves is
Transverse waves have particle vibrations perpendicular to wave direction; longitudinal waves have parallel vibrations.
If the speed of sound at 0°C is 331ms⁻¹, what is it at 50°C?
v = v_0 * √(T/T_0). v_0 = 331ms⁻¹, T_0 = 273K, T = 323K. v = 331 * √(323/273) ≈ 353ms⁻¹.
A sonometer wire has a fundamental frequency of 256Hz. What is the frequency of the third overtone?
Third overtone is the fourth harmonic: 4 * 256 = 1024Hz.
A 2m tall man stands 4m from a pinhole camera with a hole-to-screen distance of 0.2m. What is the image height?
Height of image / height of object = image distance / object distance. h_i / 2 = 0.2 / 4 → h_i = (0.2 / 4) * 2 = 0.1m.
A ray passing through the principal focus of a convex mirror is reflected
A ray through the focus of a convex mirror reflects parallel to the principal axis.
A charge of 2.0 x 10⁻⁷C moves at 4.0 x 10⁻²ms⁻¹ perpendicular to a magnetic field. If the force is 4.0 x 10⁻⁹N, what is the field strength?
F = qvB. B = F / (qv) = (4.0 x 10⁻⁹) / (2.0 x 10⁻⁷ * 4.0 x 10⁻²) = 5.0 x 10⁻³T.
A 0.5m conductor moves at 20ms⁻¹ at 45° to a 2.0T magnetic field. What is the induced e.m.f.?
e.m.f. = Blv sinθ = 2.0 * 0.5 * 20 * sin(45°) = 20 * 0.707 ≈ 7.07V.
Using X-rays to locate a swallowed object is an example of
Locating a foreign object with X-rays is diagnostic, identifying the issue.
Which particle is unaffected by electric and magnetic fields?
Gamma rays are neutral and not deflected by electric or magnetic fields.
In the photoelectric effect, the number of emitted electrons depends on
Electron emission rate is proportional to light intensity, which determines photon flux.
The particle nature of light is shown by
The photoelectric effect demonstrates light as photons, supporting its particle nature.
What is the energy of a photon with a wavelength of 2.0 x 10⁻¹⁰m?
E = hc/λ. h = 6.63 x 10⁻³⁴ Js, c = 3.0 x 10⁸ ms⁻¹, λ = 2.0 x 10⁻¹⁰m. E = (6.63 x 10⁻³⁴ * 3.0 x 10⁸) / (2.0 x 10⁻¹⁰) ≈ 9.95 x 10⁻¹⁶J.
The bond in a silicon crystal is
Silicon forms covalent bonds, sharing electrons in a crystalline lattice.
A body accelerates uniformly from rest at 2ms⁻² for 5s. What is its final velocity?
v = u + at. u = 0, a = 2ms⁻², t = 5s. v = 0 + 2 * 5 = 10ms⁻¹.
What is the momentum of a 5kg object moving at 3ms⁻¹?
Momentum = mv = 5 * 3 = 15kgms⁻¹.
The work done to stretch a spring by 0.1m, with a spring constant of 200Nm⁻¹, is
Work = (1/2)kx² = 0.5 * 200 * (0.1)² = 0.5 * 200 * 0.01 = 1.0J.
A 1000kg car accelerates from 10ms⁻¹ to 20ms⁻¹ in 5s. What is the average power?
ΔKE = (1/2)m(v² - u²) = 0.5 * 1000 * (20² - 10²) = 500 * (400 - 100) = 150,000J. Power = ΔKE/t = 150,000 / 5 = 30,000W = 30kW.
The pressure of a gas increases with
By the ideal gas law (PV = nRT), pressure increases with temperature at constant volume.
A bimetallic strip bends when heated due to
Different metals expand at different rates, causing the strip to bend.
The frequency of a wave is 50Hz, and its wavelength is 2m. What is its speed?
Speed = frequency * wavelength = 50 * 2 = 100ms⁻¹.
A convex lens has a focal length of 20cm. An object is placed 40cm from the lens. What is the image distance?
Lens formula: 1/f = 1/u + 1/v. f = 20cm, u = 40cm. 1/20 = 1/40 + 1/v → 1/v = 1/20 - 1/40 = 1/40. v = 40cm.
A current of 2A flows through a 10Ω resistor. What is the power dissipated?
Power = I²R = 2² * 10 = 4 * 10 = 40W.
The half-life of a radioactive substance is 12 hours. What fraction remains after 36 hours?
Number of half-lives = 36 / 12 = 3. Fraction remaining = (1/2)³ = 1/8.
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