NED Admission Test Physics Flashcards

24 sample cards from the Physics deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. How do you find the magnitude and direction of a vector from its components Aₓ and Aᵧ?

   Magnitude A = √(Aₓ² + Aᵧ²); Direction θ = tan⁻¹(Aᵧ/Aₓ) measured from the x-axis.

2. What are the maximum and minimum possible resultants of two vectors of magnitudes A and B?

   Maximum = A + B (when they are parallel, θ = 0°); Minimum = |A − B| (when they are antiparallel, θ = 180°).

3. Write the three equations of motion for uniform acceleration.

   v = u + at; s = ut + ½at²; v² = u² + 2as, where u = initial velocity, v = final velocity, a = acceleration, s = displacement, t = time.

4. What is the difference between distance and displacement?

   Distance is the total path length travelled (scalar, always positive). Displacement is the straight-line change in position from start to finish (vector, with direction).

5. What is the difference between speed and velocity?

   Speed is the rate of change of distance (scalar). Velocity is the rate of change of displacement (vector, with direction).

6. What is the displacement of a freely falling body, and what value of acceleration is used?

   For free fall: s = ½gt² (starting from rest), using acceleration g ≈ 9.8 m/s² directed downward (air resistance neglected).

7. How is distance found from a velocity–time graph?

   The distance (or displacement) travelled equals the area under the velocity–time graph.

8. What does the slope (gradient) of a velocity–time graph represent?

   The slope of a velocity–time graph represents acceleration.

9. What is projectile motion and what are its two independent components?

   Projectile motion is two-dimensional motion under gravity alone. It has a horizontal component with constant velocity (zero acceleration) and a vertical component with constant downward acceleration g; the two are independent.

10. Write the formulas for time of flight, maximum height, and range of a projectile launched at angle θ with speed u.

    Time of flight T = (2u·sinθ)/g; Maximum height H = (u²·sin²θ)/(2g); Range R = (u²·sin2θ)/g.

11. At what launch angle is the range of a projectile maximum, and what is that range?

    The range is maximum at θ = 45°, where R_max = u²/g.

12. What is the shape of a projectile's trajectory and the velocity at maximum height?

    The trajectory is a parabola. At maximum height the vertical velocity is zero and only the horizontal component (u·cosθ) remains.

13. Define relative velocity.

    The relative velocity of object A with respect to object B is the velocity of A as observed from B: v_AB = v_A − v_B (vector subtraction).

14. Two cars move in the same direction at velocities v₁ and v₂. What is their relative velocity?

    v_rel = v₁ − v₂ (the difference), since they move in the same direction.

15. Two cars move toward each other at velocities v₁ and v₂. What is their relative velocity of approach?

    v_rel = v₁ + v₂ (the magnitudes add), because they move in opposite directions.

16. State Newton's First Law of Motion.

    A body remains at rest or in uniform motion in a straight line unless acted upon by a net external force (the law of inertia).

17. State Newton's Second Law of Motion and its equation.

    The rate of change of momentum of a body is directly proportional to the applied force and in its direction: F = ma (or F = dp/dt).

18. State Newton's Third Law of Motion.

    For every action there is an equal and opposite reaction; the forces act on two different bodies.

19. Define inertia and state what it depends on.

    Inertia is the tendency of a body to resist any change in its state of rest or uniform motion. It depends on (is measured by) the body's mass.

20. Define linear momentum and give its SI unit.

    Linear momentum is the product of a body's mass and velocity: p = mv. It is a vector, with SI unit kg·m·s⁻¹ (equivalent to N·s).

21. Define impulse and state its relationship to momentum.

    Impulse is the product of force and the time for which it acts: J = F·Δt. The impulse–momentum theorem states impulse equals the change in momentum: F·Δt = Δp = m(v − u).

22. State the law of conservation of linear momentum.

    If no net external force acts on a system, its total linear momentum remains constant: total momentum before = total momentum after an interaction.

23. Compare elastic and inelastic collisions.

    In an elastic collision both momentum and kinetic energy are conserved. In an inelastic collision momentum is conserved but kinetic energy is not (some converts to heat/sound/deformation); in a perfectly inelastic collision the bodies stick together.

24. Define work done by a force, give its formula and condition for zero work.

    Work = force × displacement in the direction of the force: W = F·s·cosθ. Work is zero when θ = 90° (force perpendicular to displacement) or when displacement is zero. SI unit: joule (J).

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