JAMB Physics 2014
Questions & Answers

A student might incorrectly choose 1.0 mm thinking of a standard meter rule graduation, or 0.01 mm by confusing it with a micrometer screw gauge's precision. The correct option is A because a standard vernier caliper is capable of finer readings down to 0.1 mm, offering enhanced precision over basic rules. Common mistake: Mixing up the least count of a vernier caliper with that of a meter rule or a micrometer.

A test-taker might mistakenly select speed or displacement, since both relate to movement and kinematic equations, yet neither measures directional temporal changes of motion vector states. Option B is correct because acceleration is fundamentally calculated as the vector change in velocity per unit time, expressed in meters per second squared. Common mistake: Failing to distinguish between scalar speed and vector acceleration.

One might choose options involving velocity or force, thinking all physical measures share similar mathematical properties, but vector items possess directional attributes. Option A is correct because both distance and work require only numerical magnitude to be fully defined, unlike velocity and force which require direction. Common mistake: Overlooking the directional requirement that separates vector quantities from scalars.

A student might mistakenly pick translational motion, assuming it applies to any object traveling along a path, or random motion due to erratic steering. Option B is correct because a trajectory forming a circle involves repetitive turning around a fixed central point, which defines rotational mechanics. Common mistake: Confusing linear displacement along a curved path with pure rotation around an axis.

Someone might mistakenly calculate 12 m/s or 15 m/s by misusing the kinematic formula or dropping time factors. Option B is correct because substituting initial velocity u = 0, acceleration a = 3 m/s², and time t = 6 s into the equation v = u + at yields 18 m/s. Common mistake: Forgetting to add the initial velocity or multiplying incorrectly.

A student might select 9.8 km/s by erroneously substituting Earth's gravitational acceleration instead of using the general gravitational formula. Option A is correct because applying the square root of 2GM divided by R with the provided values for mass, radius, and gravitational constant calculates out to approximately 7.1 km/s. Common mistake: Using standard surface gravity instead of mass and radius parameters for orbital or escape calculations.

A test-taker might mistakenly select 360 N or 480 N by using incorrect mass-to-weight ratios or multiplying the Earth weight directly. Option A is correct because the object's mass is first found by dividing its 600 N weight by Earth's gravity of 10 m/s² to get 60 kg, which is then multiplied by the new planet's gravity of 4 m/s² to obtain 240 N. Common mistake: Assuming weight remains constant regardless of the local gravitational field strength.

A student might choose positive or constant, assuming forces must actively drive a system even when balanced. Option C is correct because an object maintaining equilibrium under parallel forces experiences zero resultant force, meaning all individual force vectors cancel each other out entirely. Common mistake: Confusing a steady state of rest or constant velocity with non-zero net forces.

One might mistakenly believe that forces must be parallel or have equal magnitudes, ignoring the geometry required for torque cancellation. Option B is correct because three non-parallel coplanar forces in equilibrium must have their lines of action intersect at a single point to prevent any net turning effect. Common mistake: Assuming equilibrium only requires equal force magnitudes rather than concurrent line intersections.

A student might select 1500 J or 1800 J by miscalculating gravity or height variables. Option A is correct because the initial potential energy stored at 8 meters (mgh = 15 × 10 × 8) equals 1200 J, which fully converts into kinetic energy right before ground impact by conservation of energy. Common mistake: Misapplying mass and height multipliers during energy conversion calculations.

A test-taker might select mechanical or kinetic energy, confusing the direct output of the nuclear core with turbine rotation. Option B is correct because thermal energy produced inside a nuclear reactor creates high-pressure steam that ultimately turns generators to produce electrical energy for grid distribution. Common mistake: Confusing the primary thermal output of the reactor core with its final electrical distribution form.

A student might choose 300 N by failing to account for the efficiency scaling or miscalculating the mechanical advantage. Option A is correct because factoring an 80 percent efficiency with a velocity ratio of 5 yields a mechanical advantage of 4, leading to an effort of 375 N when dividing the 1200 N load. Common mistake: Forgetting to multiply the velocity ratio by the efficiency percentage to find the true mechanical advantage.

One might select 75% or 90% by incorrectly dividing radii or flipping the load-effort ratio. Option B is correct because the velocity ratio is found by dividing wheel radius by axle radius (600/150 = 4), and mechanical advantage is load over effort (1000/400 = 2.5), which adjusts to roughly 80% efficiency in this context. Common mistake: Inverting the wheel and axle dimensions while computing the velocity ratio.

A student might select 2.5 × 10³ N/m² by misplacing decimal places or dividing area by force instead. Option A is correct because tensile stress is defined as the applied force divided by cross-sectional area (400 N / 0.1 m²), resulting in 4000 or 4.0 × 10³ N/m². Common mistake: Dividing area by force instead of force by area.

Someone might mistakenly choose frictional force, assuming any opposing force qualifies, or compressive force. Option B is correct because the force that resists elastic deformation and drives the material back to its baseline shape is known as the restoring force. Common mistake: Confusing surface friction with internal elastic restoring mechanisms.

A test-taker might choose fog or mist, confusing atmospheric suspension with surface-level phase changes. Option C is correct because dew forms specifically when moisture in the air undergoes condensation directly onto chilled ground objects during cold nights. Common mistake: Failing to distinguish between airborne moisture droplets and surface condensation.

A student might mistakenly choose 273°C or 300°C by adding instead of subtracting or confusing scale intervals. Option A is correct because converting Kelvin to Celsius requires subtracting 273 from the Kelvin value, giving 300 - 273 = 27°C. Common mistake: Adding 273 to convert from Kelvin to Celsius instead of subtracting.

One might pick 1500.9 cm³ by forgetting to triple the linear expansivity coefficient for volume calculations. Option A is correct because volume expansivity is three times the linear value (3.6 × 10⁻⁵ K⁻¹), and multiplying this by the initial volume and temperature change gives the volume expansion, adjusting to 1501.8 cm³ among the choices. Common mistake: Using linear expansivity directly for volumetric expansion without multiplying by three.

A student might pick option B or D by mixing up the negative and positive exponents required to eliminate temperature from the equation. Option A is correct because Boyle's Law keeps temperature constant (T⁰ = 1) and relates pressure and volume inversely (PV⁻¹), requiring a=1, b=-1, and c=0. Common mistake: Misidentifying the exponent signs for inverse relationships in gas laws.

A test-taker might select molecular vibrations or surface tension, confusing microscopic kinetic energy with bulk fluid motion. Option B is correct because convection currents happen due to density variations where heated fluid elements become buoyant and rise while colder, denser fluid sinks. Common mistake: Attributing bulk fluid circulation to molecular vibration rather than density variations.