Mechanics flashcards

Mechanics covers the motion of objects and the forces that cause or change that motion. Students must understand displacement, velocity, acceleration and how to use kinematic equations for uniform acceleration. Newton's three laws of motion explain how forces affect objects, while the concepts of momentum and impulse describe how forces act over time. Work, energy and power link forces to energy transfers, and the principle of conservation of energy underpins much of the analysis. Projectile motion, friction, and the distinction between scalar and vector quantities are all essential. Students should be comfortable resolving vectors into components, drawing free-body diagrams, and applying conservation of momentum to collisions. Understanding the difference between elastic and inelastic collisions, and being able to interpret motion graphs accurately, are key skills throughout this topic.

1. Card 1

   What is the difference between distance and displacement?

   Distance is the total path length travelled (scalar), while displacement is the straight-line change in position with direction (vector).

2. Card 2

   Define velocity and state whether it is a scalar or vector.

   Velocity is the rate of change of displacement with time. It is a vector quantity, meaning it has both magnitude and direction.

3. Card 3

   State Newton's First Law of motion.

   An object remains at rest or moves with constant velocity unless acted upon by a resultant external force, demonstrating the principle of inertia.

4. Card 4

   What does Newton's Second Law state mathematically?

   The resultant force equals mass times acceleration: F = m x a. This means acceleration is directly proportional to the resultant force on an object.

5. Card 5

   State Newton's Third Law of motion.

   When object A exerts a force on object B, object B exerts an equal and opposite force on A. These are called Newton's third law pairs and act on different objects.

6. Card 6

   What is impulse and how does it relate to momentum?

   Impulse equals force multiplied by time (F x t) and is equal to the change in momentum of an object. Units are newton-seconds (N s).

7. Card 7

   State the principle of conservation of momentum.

   The total momentum of a closed system remains constant provided no external resultant force acts. This applies to all collisions and explosions.

8. Card 8

   What distinguishes an elastic collision from an inelastic one?

   In an elastic collision both momentum and kinetic energy are conserved. In an inelastic collision momentum is conserved but kinetic energy is not.

9. Card 9

   How do you find displacement from a velocity-time graph?

   Displacement equals the area under a velocity-time graph. If the area is below the time axis, that portion represents displacement in the opposite direction.

10. Card 10

    What are the two components of projectile motion?

    Horizontal motion has constant velocity (no air resistance), while vertical motion has constant downward acceleration due to gravity (g = 9.8 m/s squared).

11. Card 11

    Define work done by a force.

    Work done equals force multiplied by displacement in the direction of the force: W = F x d x cos(theta). It is measured in joules (J).

12. Card 12

    What is the work-energy theorem?

    The net work done on an object equals its change in kinetic energy. This links force and displacement directly to changes in an object's energy of motion.

• Students often confuse mass and weight, forgetting that weight is a force (W = m x g) measured in newtons, while mass is a scalar measured in kilograms.
• A common error is assuming that a stationary object has no forces acting on it, when in fact forces may be balanced, giving a zero resultant force.
• Many students forget that Newton's third law pairs act on different objects, so they cannot cancel each other out on a single free-body diagram.

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