Course

O Level Physics: Mechanics, Thermal Physics and Momentum (5054)

Name: O Level Physics: Mechanics, Thermal Physics and Momentum (5054)
Price: 1999 BDT

5054 sections 1 and 2: measurement, motion, forces, momentum, energy, pressure and thermal physics taught through models you can move.

100 lessons17h 11mEnglish

What you'll learn

Work each 5054 topic through a model you control, rather than a worked example you watch
Predict before you calculate, so a wrong idea is caught while it is still cheap
Read and draw the graphs Paper 1 and Paper 2 ask for
Answer in the exam register: state, describe, explain, calculate and determine
Finish every chapter with one full exam question worked end to end

Requirements

Junior secondary science, or Class 8 general science
Comfortable with fractions, decimals and simple rearranging

Course content

100 lessons · 17h 11m

1.1 · Physical quantities and measurement techniques

Write every quantity as a number and a unit, measure lengths, volumes and times with the right instrument, time many swings for one period, and tell scalars from vectors before adding two vectors at right angles.

0/12

Physical quantities and units

A quantity is a number times a unit. Each prefix is a power of ten, so 17.5 cm is 0.175 m.

Preview12m 2.

Measuring length with tapes and rulers

Pick the instrument for the size, keep your eye above the mark, and subtract the start reading.

Preview12m

Reading an analogue micrometer

Sleeve plus thimble gives the reading to 0.01 mm. Close it first and take away any zero error.

14m

Measuring volume with a measuring cylinder

Read the bottom of the meniscus at eye level. A stone’s volume is the rise in the water level.

12m

Measuring time intervals

Clocks for minutes, stopwatches for seconds, light gates for fractions of a second. Your reaction time is the weak link.

12m

Measuring multiples: small distances and short times

Measure 200 sheets or 20 swings, then divide. The error in reading is shared out over them all.

14m

Scalars and vectors

A scalar has size only. A vector has size and direction: 30 m east and back again is 60 m walked but 0 m moved.

12m

The resultant of two vectors at right angles: by calculation

Draw the two vectors head to tail. Pythagoras gives the size of the resultant and tan gives its direction.

14m

The resultant of two vectors at right angles: by scale drawing

Choose a scale, draw the arrows head to tail, then measure the resultant with a ruler and a protractor.

14m

10.

Physical quantities and measurement: practice

A timed drill of mixed questions: prefixes, scale readings, multiples, scalars and vectors.

11.

Physical quantities and measurement: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

12.

Physical quantities and measurement: summary

The key points, the methods and the common mistakes on one screen, with cards to revise from.

1.2 · Motion

Speed, velocity and acceleration, then the two graphs of motion: the gradient gives speed or acceleration, and the area under a speed-time graph gives the distance. Ends with free fall at 9.8 m/s².

0/15

Speed

Speed is the distance travelled each second: Sara runs 100 m in 12.5 s, so 8.0 m every second.

Preview11m 2.

Average speed

Total distance over total time, stops included. Never take the mean of two speeds.

Preview11m

Velocity

Velocity is speed in a direction. One lap of the track is 400 m of distance but zero displacement.

11m

Acceleration

Acceleration is the change in velocity each second: the bus gains 1.5 m/s every second, so a = 1.5 m/s².

12m

Deceleration

Slowing down is a negative acceleration: the bus goes from 12 m/s to 0 in 6.0 s, so a = −2.0 m/s².

11m

Uniform and non-uniform acceleration

The bus gains the same speed every second; Sara gains less and less as she reaches her top speed.

11m

Distance-time graphs

Flat means at rest, a straight slope means constant speed, and a curve means the speed is changing.

12m

Speed from a distance-time graph

The gradient is the speed: rise over run on a straight line, or the gradient of a tangent on a curve.

12m

Speed-time graphs

On a speed-time graph a flat line means constant speed, not rest. A straight slope means constant acceleration.

12m

10.

Acceleration from a speed-time graph

The gradient of a speed-time graph is the acceleration, and a downhill line gives a negative one.

12m

11.

Distance from a speed-time graph

The area under a speed-time graph is the distance: two triangles and a rectangle give the bus 324 m.

13m

12.

Acceleration of free fall

Near the Earth a falling object gains about 9.8 m/s every second, whatever its mass, if air resistance is small.

12m

13.

Motion: practice

A timed drill of mixed questions: speed, velocity, acceleration, both graphs and free fall.

14.

Motion: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

15.

Motion: summary

The key points, the three equations, the graph rules and the common mistakes on one screen.

1.3, 1.5.1-1.5.2 · Mass, weight and forces

Tell mass from weight and measure both, name the forces on an object and draw them, add them to a resultant, then use Newton's laws, friction, drag and stopping distances.

0/16

Mass and inertia

Mass is the amount of matter in an object. More mass means the object resists a change in its motion more.

Preview10m 2.

Weight and gravitational field strength

Weight is the pull of gravity on a mass. On Earth each kilogram is pulled with 9.8 N, so W = mg.

Preview12m

Measuring mass and weight

A balance finds mass and a force meter finds weight. Zero each one before you read it.

11m

Types of force

Every force is a push or a pull between two objects. Learn the nine names the syllabus uses.

10m

Free-body diagrams

Draw one object alone and give every force on it an arrow that starts on the object.

11m

Resultant force

Forces along one line add like numbers with signs. Choose a positive direction and add.

11m

Newton's first law

With no resultant force, an object stays at rest or keeps a steady speed in a straight line.

11m

Resultant force, mass and acceleration (F = ma)

A resultant force makes a mass accelerate: F = ma. Always use the resultant, never one force alone.

12m

Newton's third law

Forces come in pairs: equal, opposite, the same type, and acting on two different objects.

11m

10.

Friction

Friction acts against sliding. It can hold a box still, it slows moving things, and it heats them.

11m

11.

Drag and terminal velocity

Drag grows with speed until it balances the weight. Then the resultant is zero and the speed stops rising.

12m

12.

Thinking distance, braking distance and stopping distance

A car keeps going while the driver reacts, then while the brakes work. Stopping distance is the two added.

11m

13.

Factors affecting thinking and braking distance

Tiredness, alcohol and drugs lengthen the thinking distance. Load, worn tyres and wet roads lengthen the braking distance. Speed lengthens both.

11m

14.

Mass, weight and forces: practice

A timed drill of mixed questions: mass or weight, which force, the resultant, F = ma and stopping distance.

15.

Mass, weight and forces: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

16.

Mass, weight and forces: summary

The key points, the equations and the common mistakes on one screen, with cards to revise from.

1.5.5-1.5.6 · Turning effect of forces and centre of gravity

A moment is force times perpendicular distance from the pivot. Balance clockwise against anticlockwise moments, find where an object's weight acts, and say why a low, wide load is hard to tip.

0/11

The moment of a force

A moment is the turning effect of a force. Push far from the hinge and a small force opens the door.

Preview10m 2.

Calculating moments

Moment = force × perpendicular distance from the pivot, in N m. Measure the distance at right angles to the force.

Preview12m

The principle of moments

A balanced seesaw has equal clockwise and anticlockwise moments. The heavier person sits nearer the pivot.

12m

Using the principle of moments

Add every moment on each side, then solve for the one you do not know. Take moments about a support to find the other support force.

13m

An experiment to verify the principle of moments

Balance a metre rule on its centre with weights on both sides. In every row of results the two moments agree.

12m

Centre of gravity

All of an object's weight can be treated as acting at one point. For a uniform shelf, that point is the middle.

11m

Finding the centre of gravity of a plane lamina

Hang the card from two holes and draw along a plumb line each time. The centre of gravity is where the lines cross.

11m

Centre of gravity and stability

An object tips over when the line down from its centre of gravity passes outside its base. Low and wide is stable.

11m

Turning effect of forces and centre of gravity: practice

A timed drill of mixed questions: units, perpendicular distance, balancing, centre of gravity and stability.

10.

Turning effect of forces and centre of gravity: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

11.

Turning effect of forces and centre of gravity: summary

The key points, the equation and the common mistakes on one screen, with cards to revise from.

1.4, 1.5.3, 1.8 · Density, elastic deformation and pressure

Find density by three methods, measure a spring constant and read a load-extension graph, then calculate pressure on a surface, in a liquid and from a barometer.

0/14

Density

Density is mass per unit volume. Two blocks of the same size can have very different masses.

Preview10m 2.

Density of a liquid and a regular solid

Measure a block with a ruler and a balance. Weigh a liquid by taking away the mass of the empty cylinder.

Preview11m

Density of an irregular solid

A stone has no sides to measure, so let it push water aside: the rise in level is its volume.

11m

Elastic deformation and the spring constant

Forces change shape. The spring constant is the force for each unit of extension: k = F/x.

11m

Load-extension graphs and the limit of proportionality

Add loads one at a time and plot the extension. The straight line ends at the limit of proportionality.

12m

Pressure

Pressure is force per unit area. The same weight on a heel presses 100 times harder than on a trainer.

11m

How pressure varies with force and area

Wide straps, tyres and snowshoes spread a force out. Pins, knives and studs squeeze it onto a tiny area.

10m

Pressure acts at right angles to a surface

Water squirts out of every hole in a bottle at 90° to the wall. The force from pressure is F = pA.

10m

Pressure beneath the surface of a liquid

Twice as deep gives twice the pressure. A denser liquid gives more. The shape of the tank does not matter.

11m

10.

Calculating the change in pressure in a liquid

The weight of a column of liquid gives Δp = ρgΔh. Ten metres of sea adds about 101 kPa.

12m

11.

The liquid barometer

The air holds up about 76 cm of mercury. Measure the column height and ρgh gives the atmospheric pressure.

11m

12.

Density, elastic deformation and pressure: practice

A timed drill of mixed questions: density, springs, pressure on a surface and pressure in a liquid.

13.

Density, elastic deformation and pressure: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

14.

Density, elastic deformation and pressure: summary

The key points, the equations and the common mistakes on one screen, with cards to revise from.

1.7.1-1.7.2, 1.7.4-1.7.5 · Energy, work and power

Name the energy stores and the ways energy moves between them, use conservation of energy, calculate kinetic and gravitational potential energy, work done, efficiency and power.

0/12

Energy stores

Energy sits in seven kinds of store, from the chemical store in a phone battery to the kinetic store of a moving bus.

Preview11m 2.

Energy transfers between stores

Energy moves between stores in four ways: by a force, by an electric current, by heating and by waves.

Preview12m

The principle of the conservation of energy

Energy is never made or destroyed. Count every store and the total at the end equals the total at the start.

12m

Kinetic energy

Ek = ½mv². The speed is squared, so twice the speed means four times the energy.

12m

Change in gravitational potential energy

ΔEp = mgΔh. Carry a box up one floor and its gravitational store grows by mass × 9.8 × height.

12m

Kinetic and gravitational potential energy together

Gravitational energy lost at the top of the slide becomes kinetic energy at the bottom, so mgh = ½mv².

13m

Work done

W = Fd. Work done is the energy a force transfers, and lifting a box shows why ΔEp = mgΔh.

12m

Efficiency

Efficiency is the useful output divided by the total input, for energy or for power. It is never more than 100%.

12m

Power

Power is work done, or energy transferred, per second. A 2000 W kettle transfers 2000 J every second.

12m

10.

Energy, work and power: practice

A timed drill of mixed questions: stores, transfers, kinetic and potential energy, work, efficiency and power.

11.

Energy, work and power: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

12.

Energy, work and power: summary

The key points, the equations and the common mistakes on one screen, with cards to revise from.

1.5.4 · Circular motion

Why a force at right angles to the motion makes an object move in a circle, and how that force depends on speed, radius and mass (described in words, without F = mv²/r).

0/6

Motion in a circular path

Steady speed but changing direction: a force at right angles to the motion, towards the centre, keeps an object on a circle.

Preview11m 2.

Force, speed and radius

A bigger inward force means a faster speed on the same circle, or a tighter circle at the same speed.

Preview12m

Mass and circular motion

A full bus needs a bigger inward force than an empty one to take the same bend at the same speed.

10m

Circular motion: practice

A timed drill of mixed cards, then eight questions on the direction of the force and what it depends on.

Circular motion: exam practice

Exam-style questions with marks, mark schemes and full worked answers in words.

Circular motion: summary

The three rules, the direction of the force and the common mistakes on one screen, with cards to revise from.

1.6 · Momentum

Momentum p = mv and its direction, conservation of momentum in collisions and explosions, impulse FΔt = Δ(mv), and force as the rate of change of momentum.

0/6

Momentum

A bus and a bicycle at the same speed: which is harder to stop? Momentum is mass times velocity.

Preview10m 2.

Momentum is a vector

Choose a positive direction. Momentum to the left is negative, and a total can be zero.

Preview11m

The principle of conservation of momentum

In a collision, the total momentum before equals the total momentum after. Two trolleys that stick together show it.

12m

Using conservation of momentum

Head-on crashes, bounces and two skaters pushing apart: the same rule with signs.

12m

Impulse

Force times contact time equals the change in momentum. Why do fielders pull their hands back?

12m

Resultant force and the rate of change of momentum

F = Δp ÷ Δt. A longer stopping time means a smaller force: seat belts, airbags and crumple zones.

12m

About the creator

8bitlesson

Cambridge O Level, A Level and university courses, taught through interactive labs.

Mentora builds the sciences and mathematics as things you can move rather than videos you watch. Cambridge O Level and A Level mathematics, physics, chemistry and accounting, a primary mathematics track, and first-year university computer science. Every lesson works a real exam question end to end.