Allied Health Sciences Entry 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. 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 the direction of the force. F = ma (or F = dp/dt).

2. State Newton's third law of motion.

   For every action there is an equal and opposite reaction. The two forces act on different bodies, are equal in magnitude, and opposite in direction.

3. Define linear momentum and state its SI unit.

   Linear momentum is the product of mass and velocity: p = mv. It is a vector. SI unit: kilogram metre per second (kg m s^-1).

4. State the law of conservation of linear momentum.

   In the absence of external forces, the total momentum of an isolated system remains constant. For a collision: m1u1 + m2u2 = m1v1 + m2v2.

5. What is the difference between an elastic and an inelastic collision?

   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). In a perfectly inelastic collision the bodies stick together.

6. Define impulse and state its relationship to momentum.

   Impulse = force x time = F t. Impulse equals the change in momentum: F t = m(vf - vi). SI unit: N s (= kg m s^-1).

7. What is projectile motion and what are the independent components of its velocity?

   Projectile motion is two-dimensional motion under gravity with constant horizontal velocity and uniformly accelerated vertical motion. Horizontal: vx = vi cos theta (constant); Vertical: vy = vi sin theta - gt.

8. Give the formulas for time of flight, maximum height, and horizontal range of a projectile launched at angle theta with speed vi.

   Time of flight T = (2 vi sin theta)/g; Maximum height H = (vi^2 sin^2 theta)/(2g); Range R = (vi^2 sin 2theta)/g.

9. At what launch angle is the horizontal range of a projectile maximum, and why?

   At 45 degrees, because R = (vi^2 sin 2theta)/g is maximum when sin 2theta = 1, i.e. 2theta = 90, theta = 45 degrees.

10. Define work done by a constant force and give its formula.

    Work = force x displacement in the direction of the force: W = F S cos theta, where theta is the angle between force and displacement. SI unit: joule (J).

11. When is the work done by a force zero, positive, or negative?

    Zero when force is perpendicular to displacement (theta = 90). Positive when force has a component along displacement (theta < 90). Negative when force opposes displacement (theta > 90, e.g. friction).

12. Define kinetic energy and give its formula.

    Kinetic energy is the energy of a body due to its motion: KE = (1/2)m v^2. SI unit: joule (J).

13. Define gravitational potential energy and give its formula near Earth's surface.

    Gravitational potential energy is the energy due to position in a gravitational field: PE = mgh, where h is height above a reference level. SI unit: joule (J).

14. State the work-energy theorem.

    The net work done on a body equals the change in its kinetic energy: W_net = (1/2)m vf^2 - (1/2)m vi^2 = delta KE.

15. State the law of conservation of energy.

    Energy can neither be created nor destroyed; it can only be transformed from one form to another. The total energy of an isolated system remains constant.

16. For a freely falling body, how does total mechanical energy behave, and write the conservation relation.

    Total mechanical energy (KE + PE) stays constant. As the body falls, PE converts to KE: mgh = (1/2)m v^2 at the bottom (ignoring air resistance), so v = sqrt(2gh).

17. Define power and give its formulas.

    Power is the rate of doing work or transferring energy: P = W/t. Also P = F v (force x velocity). SI unit: watt (W) = J s^-1.

18. Define efficiency and give its formula.

    Efficiency = (useful output energy or power / total input energy or power) x 100%. It is always less than 100% due to energy losses (e.g., friction, heat).

19. Define angular velocity and state the relation between linear and angular velocity.

    Angular velocity omega is the rate of change of angular displacement: omega = theta/t (rad s^-1). Relation: v = r omega, where r is the radius.

20. What is centripetal acceleration and centripetal force? Give their formulas.

    Centripetal acceleration is directed toward the centre of a circular path: a = v^2/r = r omega^2. Centripetal force is the force causing it: F = m v^2/r = m r omega^2, directed toward the centre.

21. Define the time period and frequency of circular motion and relate them to angular velocity.

    Time period T is the time for one revolution; frequency f = 1/T is revolutions per second. Angular velocity omega = 2 pi f = 2 pi / T.

22. Give the formula for the rotational kinetic energy of a rigid body and define the moment of inertia.

    Rotational KE = (1/2) I omega^2, where I is the moment of inertia (I = sum of m r^2) and omega is angular velocity. Moment of inertia is the rotational analogue of mass.

23. State the equation of continuity for an incompressible fluid and what it expresses.

    A1 v1 = A2 v2 (Av = constant), where A is cross-sectional area and v is fluid speed. It expresses conservation of mass: where the pipe is narrow the fluid flows faster.

24. State Bernoulli's equation and what it represents.

    P + (1/2)rho v^2 + rho g h = constant, where P is pressure, rho is density, v is speed, h is height. It expresses conservation of energy for an ideal (non-viscous, incompressible, steady) fluid flow: higher speed corresponds to lower pressure.

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