كيف يحسب الرقم الهيدروجيني pH للمحاليل؟ How to calculate pH and pOH?

يحسب الرقم الهيدروجيني بالعلاقة: pH = -log[H⁺]، وللمحاليل المائية عند 25°C: pH + pOH = 14. إذا كان pH 7 فالمحلول قاعدي. [الصيغة الرمزية الموزونة: pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴]

Theme A — Space, Time and Motion

A.1 Kinematics — IB Physics SL Revision Notes & Topical Questions

5 min read 10 parts Lesson 2 of 41 1 quiz

📚 IB Physics SL Hub / Topical Revision

Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution

pH = -log[H⁺]  |  pOH = -log[OH⁻]  |  pH + pOH = 14  |  [H⁺][OH⁻] = 10⁻¹⁴

Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14

Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.

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Lesson summary

A.1 Kinematics — IB PHYSICS SL notes: Describe and analyse motion using displacement, velocity, acceleration, equations of motion, graphs and projectile motion.Distance — how far an object travels; a scalar with no direction.Displacement — how far an object is from its starting p…

Instantaneous velocity
What the symbols mean
Time of flight
Maximum height
Fluid resistance (viscous drag)
Terminal speed

Part 1 of 8Distance and displacement

Distance

Distance how far an object travels; a scalar with no direction.

Displacement

Displacement how far an object is from its starting position, with direction;
- the change in position and a vector.

The student's route to school gives a long distance but a straight-line displacement from home to school.

If athletes run 300 m round a 400 m track, the distance is 300 m but the displacement is 100 m; after a full lap it is zero.

Part 2 of 8Speed and velocity

Speed

Speed distance travelled per second; a scalar in m s⁻¹.
Average speed = total distance ÷ time taken.

Velocity

Velocity the rate of change of displacement; a vector, so it can be negative.

Velocity is speed in a given direction; cars with the same speed in different lanes have different velocities.

Instantaneous velocity

Instantaneous velocity the velocity at a moment; the gradient of a tangent to the displacement-time graph.
A straight line shows constant velocity; a curve shows acceleration.

Average velocity = total displacement ÷ total time; for constant acceleration it is (u + v) ÷ 2.

Part 3 of 8Acceleration

Acceleration

Acceleration the rate of change of velocity; a vector in m s⁻².
a = Δv ÷ Δt, where Δv = v − u.

Positive when speeding up in the positive direction, negative when slowing down (deceleration) or accelerating in the negative direction.

Instantaneous acceleration is the gradient of a tangent on a velocity-time graph.

Part 4 of 8Kinematic (suvat) equations

What the symbols mean:

They describe motion with constant (uniform) acceleration and link s, u, v, a and t.

v = u + at
What the symbols mean: v = final velocity (m s⁻¹) · u = initial velocity (m s⁻¹) · a = acceleration (m s⁻²) · t = time (s)
s = ut + ½at²
What the symbols mean: s = displacement (m) · u = initial velocity (m s⁻¹) · a = acceleration (m s⁻²) · t = time (s)
v² = u² + 2as
What the symbols mean: v = final velocity · u = initial velocity (m s⁻¹) · a = acceleration (m s⁻²) · s = displacement (m)
s = ½(u + v)t
What the symbols mean: s = displacement (m) · u = initial velocity · v = final velocity (m s⁻¹) · t = time (s); (u + v)/2 is the average velocity

Key phrases:

Starts from rest means u = 0.
Falling due to gravity means a = g = 9.81 m s⁻².
Constant acceleration in a straight line signals the equations apply.

Method:

List the known and unknown variables and any implied values.
Choose the equation containing the quantities listed.
Convert to SI units, substitute and rearrange.

Choose one positive direction and keep to it for all vectors.

Part 5 of 8Motion graphs

Graph	Gradient	Area	Other features
Displacement-time	Velocity	Meaningless	Straight line = constant velocity; curve = acceleration; flat = rest
Velocity-time	Acceleration	Change in displacement	Straight line = uniform acceleration; curve = non-uniform; flat = constant velocity
Acceleration-time	Meaningless	Change in velocity	Horizontal line = constant acceleration

Part 6 of 8Bouncing ball

Gravity acts downward throughout, so the acceleration is constant (no air resistance).

At the highest point the ball momentarily has zero velocity, and the velocity changes from positive to negative.

At the lowest point the velocity changes instantly from negative to positive with the same speed.

The ball reaches the same height every bounce when air resistance is ignored.

Part 7 of 8Projectile motion

Projectile

Projectile a particle moving freely (non-powered) under gravity in two dimensions.
Fluid resistance is negligible and g is constant.

Launch velocity u at angle θ resolves into u cos θ (horizontal, constant) and u sin θ (vertical).

Horizontal and vertical motion are independent and only the time is shared.

Time of flight

Time of flight time in the air; the time to maximum height is half the total.

Maximum height

Maximum height where the vertical velocity is zero.

Range

Range the horizontal distance travelled.

Part 8 of 8Fluid resistance and terminal speed

Fluid resistance and terminal speed

Fluid resistance (viscous drag)

Fluid resistance (viscous drag) the resistive force from a gas or liquid;
- a type of friction opposing motion and transferring energy to the surroundings.
Lift is perpendicular to the flow; drag increases with speed.

With air resistance a projectile has a smaller range, lower maximum height, shorter flight time and a path no longer a parabola, steeper on the way down.

Terminal speed

Terminal speed as speed rises, drag rises, the resultant force falls, and when drag equals weight acceleration is zero.
A heavier object reaches a higher terminal speed.
A parachute makes the skydiver decelerate to a lower terminal speed.

Key terms

Term	Meaning
Displacement	Change in position in a stated direction.
Velocity	Rate of change of displacement.
Acceleration	Rate of change of velocity.
Instantaneous velocity	Velocity at one moment, from the gradient of a tangent.
Projectile	Object moving freely under gravity in two dimensions.
Fluid resistance	Drag force from a fluid opposing motion.
Terminal speed	Constant speed when drag equals weight.

Avoid these mistakes

Taking distance as displacement — displacement has direction and can be zero.

Using the kinematic equations when acceleration is not constant.

Mixing positive and negative directions for vectors.

Confusing the sin and cos components of a projectile's velocity, or not converting units to metres.

Saying a skydiver moves upwards when the parachute opens — they decelerate to a lower terminal speed.

Last updated: 18 October 2026

Physics 0625 & 9702 SUVAT Mastery Graph Interpretation

Constant Acceleration Equations (SUVAT) & Slopes

v = u + at | s = ut + ½at² | v² = u² + 2as | s = ½(u + v)t

Displacement-Time Graph: Gradient = Velocity (curve = accelerating).
Velocity-Time Graph: Gradient = Acceleration; Area under curve = Distance travelled / Displacement.
Free Fall in vacuum: a = g ≈ 9.81 m/s² downwards (air resistance negligible).