1. MOTION
The Four-stroke Petrol Engine
Vehicles without Engines
1. Many vehicles do not use engines to move about e.g. bicycles,
bullock carts and wheelbarrows.
2. The bicycle uses human energy to paddle and move it.

2. Vehicles with Engines
3. Many types of vehicles have engines which move them.
2. The four-cylinder engine is commonly used in motor vehicles.
3. A fuel is burnt in the engine to move the pistons. The up and
down motion of the pistons causes the shafts in the vehicle to
rotate and the wheels to turn. This makes the vehicle to move.

6. The Two-stroke Petrol Engine
Two-stroke Petrol Engine
5. It is used for small machines e.g. motor boats, motorcycles and
lawn mowers.
2. It is an inlet tube for the petrol-air mixture to go in and an outlet
tube for exhaust gases to up escape.
3. The inlet tube and the outlet tube are open or closed by the piston
moving up and down.

8. Upward stroke
1. The piston moves up the cylinder.
2. The inlet tube opens and the petrol-air
mixture enters the cylinder due to lower pressure in the cylinder.
3. Piston closes the outlet tube.
4. Petrol-air mixture above the piston is compressed by the
rising piston.
Downward stroke
1. When the piston reaches the top of the cylinder, a spark fired by the
spark plug ignites the petrol-air mixture in the upper part of the
cylinder.
2. The force of the expanding gases pushes the piston down, opening
the outlet tube and allowing the exhaust gases to escape.
3. The piston closes the inlet tube as it is moving down and forces
petrol-air mixture into the upper part of the cylinder through a transfer
passage.

10. Relationship between Operation of the engine and motion of the Vehicle
Transfer of Motion in a Car
5. When the engine of a car is started, the pistons move up and
down and rotate a crankshaft.
2. When the gear is engaged, the crankshaft is connected to the
transmission system (clutch and gearbox) and a drive shaft.
3. The rotating crankshaft rotates the drive shaft, the differential
gear, and the wheel axle, causing the wheels to turn.

13. The Gear System
Low gear (force multiplier)
5. When a low gear is used, a small gear (driving wheel) is used to
turn a large gear (driven wheel).
2. The large gear turns more slowly but exerts a greater force.
3. A low gear is used when the car is starting to move or going up a
deep slope.

14. High gear (speed multiplier)
1. When a high gear is engaged, a large gear (driving wheel) is used
to turn a small gear (driven wheel).
2. The small gear rotates faster (more speed) but has less force.
3. A high gear is used to increase speed.

15. Clutch, Foot Brake and Accelerator
1. The clutch is used when the driver wishes to change gear.
Modern cars have an automatic system for changing gears.
2. The foot brake is used for slowing down or stopping the car.
3. The accelerator is used to increase fuel to the engine and so
increases the speed of the car.

16. Speed, Velocity and Acceleration
Speed = kelajuan

17. Velocity = halaju

18. Acceleration = pecutan

24. Inertia
What is Inertia?
5. Inertia is the tendency of a body to maintain its state of
rest or uniform motion in a straight line unless it is
acted upon by a force.
2. Any body with mass has inertia.

25. Stationary inertia
Stationary inertia is the inertia possessed by a body at
rest.
(e)We need to use a force to push an object, because the
object’s stationary inertia resists motion.
(b) When the cardboard is hit out of its position quickly,
the coin falls into the glass. The coin tends to remain at
rest in its original position because of its stationary
inertia.
(c) When block R is hit out of the stack quickly,P and Q
move down vertically due to their stationary inertia.

27. Moving inertia
Moving inertia is possessed by a moving object. It resists any force
trying to slow it down, make it go faster or change its direction
of motion.
(e)When a moving car stops suddenly, the passengers in the car
are thrown forward because the moving inertia in the
passengers continue to move them forward.
(b) When an electric fan is switched off the blades continue to
rotate for some time due to the moving inertia of the rotating
blades.
(c) Trains, cars, aeroplanes and ships which are moving cannot
stop at once when the brakes are applied or the engines are
switched off. They continue to move for some distance before
stopping because of their moving inertia.

28. Relations between Mass and Inertia
3. The tin with the bigger mass (tin filled with sand) requires a larger
force to make it swing or to stop it from swinging.
2. This shows a body with a large mass has more inertia than a body
with a small mass.

29. Safety Measures Used in Vehicles to Reduce the Negative
Effects of Inertia
3. Seat belts prevent the driver and passengers from being
thrown forward in a collision.
2. Air bags prevent injury to the driver.
3. The collapsible steering column prevent injury to the
driver.
4. Headrests prevent the heads of passengers from being
jerked backwards.
5. Bumpers in the front and the back absorb the collision
force.
6. The strong body frame of the car protects the passengers.

32. Applications of Momentum
3. A falling pile driver has a large momentum because of
its huge mass and high velocity so that it can hit a
concrete pillar into the ground.
2. A bullet fired from a gun has high penetrating power
because of the high velocity of the bullet.
3. A steam roller has a large momentum for rolling a
surface because of its huge mass.

33. 4. Gases escaping backward from a rockets (action)
creates a forward momentum (reaction) which pushes
the rocket forward.
5. A motor vehicle has safety features to protect the
driver and the passengers from the effect of the cars
high momentum in case of an accident

34. Principle of Conservations of Momentum
Conservation of Momentum
4. When two or more bodies collide with one another, the
total momentum before the collision is equal to the
total momentum after the collision.
Total momentum before collision = Total momentum
after collision
2. In an elastic collision the bodies separate after
collision.
3. In an inelastic collision, the bodies stick together after
collision.

35. Worked example
Trolley A collides with trolley B. After the collision the
two trolleys become attached and move together.
Calculate the velocity of the joined trolleys.

38. Experiment on Conservation of Momentum
3. When match sphere P is pulled aside and released, it
swings back, hits sphere Q and stops.
2. The momentum of P is transferred to Q. But Q cannot
move because it is sandwiched in the middle.
3. So the momentum of Q is transferred to sphere R.

39. 4. Sphere R swings outwards at the same velocity as
sphere P.
5. This process is repeated with P and R swinging
alternately, until the energy of the swinging spheres is
lost due to resistance and friction with the air.
6. A Newton’s cradle usually has four or five metal
spheres.

42. Applications of Pressure
3. Some tools are designed to exert a large pressure by
having the force act on a small area (Table A).
2. Some gadgets and machines are designed to reduce
the pressure on a surface by having the force act on
a large area (Table B).

44. Principle of the Hydraulic System
Transmission of Pressure in a Liquid
1. Pascal’s Principle
The pressure exerted on a liquid in an enclosed container
is transmitted equally through the liquid in all directions.
2. This principle is used in the hydraulic system.

45. The Hydraulic Brake
3. When the driver’s foot pressses on the brake pedal, the
pressure exerted on the brake fluid is transmitted
unchanged to the four wheel cylinders.
2. This pressure acting on a large of the piston in the
cylinder produces a large force on the piston.
3. This force pushes the brake pads outwards to press on
the rotating drum or rotating disc and slow down or
stop the motor vehicle.

49. The Hydraulic Jack
3. A hydraulic jack uses a small force to lift a
compressor very large force such as a motor car.
2. When the compressor is switched on, the air pressure
on the small cylinder, causing the large piston to rise.
3. The pressure on the oil in the small piston is
transmitted unchanged to the large cylinder
4. This pressure acting on a large surface of the large
piston produces a big force which pushes the car up.

51. Motion of Vehicles in Water
Principle of Operation of Vehicles in Water
Vehicles without engines
7. Sampans and canoes are moved through water by
using human energy.
2. Sailing ships are moved by using the kinetic energy of
wind.

52. Ship
3. A ship is driven by an engine
which turns the propellers.
2. The turning propellers push
the water behind (action) and
causes a forward momentum
(reaction) which drives the ship
forward.
3. The rudder of the ship controls
the direction of motion of the
ship.

53. Hovercraft
2. A hovercraft moves on a cushion of air on the surface of
the sea.
2. The engine turns the fans which produce the cushion of air
to lift the hovercraft from the sea.
3. The large fans on top of the hovercraft produce a strong
backward wind (action) which causes an equally strong
forward momentum in (reaction) that pushes the boat
forward.

54. Hydrofoil
2. The lower surface of a hydrofoil has wing-shaped
structures called hydrofoils.
2. At a certain speed, the hydrofoils get lifted above the
water surface (aerofoil principle) and the boat moves
faster because of reduced friction with the water.

55. Archimede’s Principle
3. When a body is immersed in a fluid (gas or liquid), it
experiences a loss in weight (up-thrust) equal to the
weight of the fluid displaced by the body.
2. When the ballast tanks of a submarine are filled with
sea water, the submarine becomes dense and
submerges in the sea.
3. When the ballast tanks are emptied, the submarine
becomes less dense and rises to the surface of the sea.
This is because the weight of the submarine is now
equal to the upthrust

57. Motion of Vehicles in Air
The Jet Engine
4. Air is sucked from the front of the engine into the
compressor and compressed so that it contains more
oxygen for its volume.
2. The hot compressed air is directed into the combustion
chamber where a fuel such as kerosene is sprayed into
it.

58. 3. The mixture of hot air and fuel burns and releases hot
exhaust gases, which escape from the back of the engine
and produce a great backward momentum (action).
4. This action causes as equally large forward momentum
(reaction) which pushes the jet plane forward.

59. The Rocket Engine
1.Liquid hydrogen and liquid oxygen are carried in the
rocket engine.
2. The hydrogen fuel burns fiercely in the oxygen in the
combustion chamber producing exhaust gases.
3.The exhaust gases escape from the back of the engine
with great backward momentum (action).

60. 4. This action causes an equally powerful forward
momentum (reaction) which pushes the rocket upwards.
5. Unlike a jet plane, a rocket can move outside the
Earth’s atmosphere because it carries its own hydrogen
and oxygen.

62. Bernoulli’s Principle and Its Application in
Aircrafts Bernoulli’s Principle