Aga Khan University Examination Board Physics (SSC IX-X) Syllabus

Define rest and motion.

A body is at rest if it does not change its position with respect to its surroundings over time; it is in motion if it changes its position with respect to its surroundings over time.

Why are rest and motion called relative states?

Because a body may be at rest relative to one observer and in motion relative to another; the state depends on the chosen reference point (frame of reference).

What is a frame of reference?

A coordinate system (set of reference points/axes) relative to which the position and motion of a body are described.

What is translatory motion and what are its two types?

Motion in which a body moves along a line so all its parts cover the same distance; its types are linear (straight line) and random (irregular, changing direction) motion. (Curvilinear motion along a curve is also translatory.)

What is rotatory motion? Give an example.

The spinning of a body about a fixed axis passing through it, where each particle moves in a circle; e.g. a spinning top or the wheel of a car about its axle.

What is vibratory (oscillatory) motion? Give an example.

To-and-fro motion of a body about a fixed (mean) position; e.g. the motion of a pendulum or the prongs of a vibrating tuning fork.

Distinguish between circular motion and rotatory motion.

In circular motion a body moves along a circular path around a point outside it (e.g. a stone tied to a string); in rotatory motion the body spins about an axis passing through itself (e.g. a wheel about its axle).

What is a scalar quantity? Give two examples.

A quantity that is completely described by magnitude only (no direction); e.g. mass, time, distance, speed, energy.

What is a vector quantity? Give two examples.

A quantity that requires both magnitude and direction to be completely described; e.g. displacement, velocity, acceleration, force.

How is a vector represented graphically?

By a directed line segment (arrow): its length (to scale) represents the magnitude and the arrowhead points in the direction of the vector.

Define distance and displacement, and state which is scalar and which is vector.

Distance is the total length of the path travelled (scalar); displacement is the shortest straight-line distance from the initial to the final position in a specified direction (vector).

Can displacement ever be zero while distance is non-zero? Explain.

Yes; if a body returns to its starting point, the distance travelled is non-zero but the displacement is zero because the initial and final positions coincide.

Define speed and give its formula and SI unit.

Speed is the distance covered per unit time (scalar); speed = distance ÷ time; SI unit is metre per second (m/s).

Define velocity and give its formula and SI unit.

Velocity is the displacement covered per unit time in a specified direction (vector); velocity = displacement ÷ time; SI unit is metre per second (m/s).

What is the difference between average speed and instantaneous speed?

Average speed is the total distance divided by the total time taken; instantaneous speed is the speed at a particular instant of time.

What is uniform velocity?

Velocity is uniform when a body covers equal displacements in equal intervals of time, i.e. both its speed and direction remain constant.

Define acceleration, give its formula and SI unit.

Acceleration is the rate of change of velocity with time (vector); a = (vf − vi) ÷ t; SI unit is metre per second squared (m/s²).

What is the difference between positive acceleration and negative acceleration (deceleration/retardation)?

Positive acceleration means velocity is increasing with time; negative acceleration (retardation) means velocity is decreasing with time.

On a distance–time graph, what does the slope (gradient) represent?

The slope of a distance–time graph represents the speed of the body; a steeper slope means a greater speed, and a horizontal line means the body is at rest.

On a velocity–time graph, what do the slope and the area under the graph represent?

The slope represents acceleration, and the area under the velocity–time graph represents the distance (displacement) travelled.

On a velocity–time graph, what does a horizontal straight line indicate?

Constant (uniform) velocity, i.e. zero acceleration.

State the three equations of uniformly accelerated motion.

vf = vi + at; S = vi·t + ½at²; 2aS = vf² − vi².

In the equations of motion, what do the symbols vi, vf, a, t and S stand for?

vi = initial velocity; vf = final velocity; a = acceleration; t = time taken; S = distance (displacement) covered.

What value of acceleration is used for a body moving freely under gravity, and what symbol represents it?

g, the acceleration due to gravity, approximately 9.8 m/s² (often taken as 10 m/s²), directed downward toward the Earth's centre.

How do the equations of motion change for a body thrown vertically upward?

Acceleration a is replaced by −g (since gravity opposes upward motion): vf = vi − gt; S = vi·t − ½gt²; 2gS = vi² − vf².

Define force and state its SI unit.

Force is an agency (push or pull) that changes or tends to change the state of rest or uniform motion of a body; its SI unit is the newton (N).

Define inertia and state which physical quantity is a measure of it.

Inertia is the tendency of a body to resist any change in its state of rest or uniform motion; mass is the measure of inertia (greater mass means greater inertia).

Define momentum, give its formula, SI unit and whether it is scalar or vector.

Momentum is the quantity of motion of a body; p = m × v; SI unit is kilogram metre per second (kg·m/s); it is a vector quantity.

State Newton's first law of motion and what it is also called.

A body at rest remains at rest and a body in uniform motion continues in uniform motion in a straight line unless acted upon by an unbalanced (net) external force. It is also called the law of inertia.

State Newton's second law of motion and give its mathematical form.

The acceleration of a body is directly proportional to the net force acting on it and inversely proportional to its mass, in the direction of the force; F = m × a (force equals rate of change of momentum).

State Newton's third law of motion and give an everyday example.

To every action there is an equal and opposite reaction; e.g. when a swimmer pushes water backward, the water pushes the swimmer forward (also a gun recoiling when fired).