1.6.1States of Matter
Drag Forces — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 5 parts Lesson 7 of 30 Unit quiz
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.
Section 1 of 5Drag and Fluids
A fluid is a gas or a liquid, and its particles are free to move around.
Fluid
- Fluid A gas or a liquid, whose particles are free to move and collide with any object passing through them.
Drag
- Drag A frictional force on an object moving through a fluid, produced by collisions with the fluid particles, which opposes the motion.
Air resistance
- Air resistance A type of drag acting on an object moving through air, produced by collisions with air particles.
Density effect
- Density effect A denser fluid produces greater drag, which is why moving through water is harder than moving through air.
Section 2 of 5Drag and Speed
The drag force increases as the object moves faster through the fluid.
1
An object moving through a fluid collides with more particles every second as its speed increases.
2
Each collision transfers momentum to the object, so the total drag force increases with the speed of the object.
3
At higher speeds the drag force is much larger, which is why running feels harder than walking on the same day.
4
The drag force always acts opposite to the direction of motion, so it slows the object down.
Section 3 of 5Effects of Drag
Effects of Drag
Deceleration
- Deceleration Drag reduces the resultant force on an object, so it slows the object when the driving force is small.
Heating
- Heating Work done against drag transfers kinetic energy to the thermal stores of the object and the fluid.
Viscosity
- Viscosity A more viscous liquid, such as washing-up liquid, produces more drag, so a marble falls through it more slowly.
Shape and area
- Shape and area A larger area facing the direction of motion increases drag, so a flat plate moves through air more slowly than a streamlined shape.
Section 4 of 5Worked Example
Question Explain why a parachutist falling at high speed experiences a larger drag force than when falling slowly.
- At higher speed, the parachutist meets more air particles every second.
- Each collision with an air particle exerts a backward force on the parachutist.
- More collisions per second means a larger total drag force, opposite to the motion.
Answer A higher speed means more air particles collide with the parachutist each second, so the drag force is larger.
Section 5 of 5Exam Checklist & Tips
1.6.1 – Key Points for the Exam
- Drag A frictional force that opposes the motion of an object moving through a fluid.
- Fluid A gas or a liquid, whose particles can move freely.
- Air resistance The drag force acting on an object moving through air.
- Friction A contact force that opposes motion between two surfaces, or a surface and a fluid.
Common Mistakes
- Saying drag occurs only in air; it occurs in any fluid, including liquids.
- Stating that drag stays constant as speed increases; the drag force increases with speed.
- Describing drag as a non-contact force; it results from collisions with fluid particles.
- Forgetting that drag acts opposite to the direction of motion.
Last updated:
\n