C8 Flashcards
Force
Pull or push upon an object
Effects of force
Cannot be seen but can be felt or observed
G f
Force of attraction between masses
N f
Force acting perpendicular to the surfaces of objects in contact
F f
Force that opposes motion when two surfaces rub against one another
E f
force produced when an object is stretched or compressed
B f
force that pushes an object upwards in a fluid
Ec f
Force of attraction or repulsion between electrostatic charges
M f
force of attraction or repulsion in a magnetic field
Magnitude of force is measured
Spring balance
Floating
Buoyant force > weight, object is less dense than the liquid
Submerging
Buoyant force < weight, object is denser than the liquid
First class lever
When the fulcrum is nearer to the load, a small effort can carry a large load.
When the fulcrum is nearer to the effort, a small movement can produce a large movement.
Second class lever
When the effort is further from the fulcrum, a small effort can carry a large load.
Third class lever
When the effort is nearer to the fulcrum, a large effort is needed to carry a small load.
FCL eg
Hammer, scissors
SCL eg
Bottle opener, wheelbarrow
TCL eg
Stapler, broom
Formula for solving lever problems
Exd= Lxd
Formula for moment of force
M(nm)=fxd
Formula for pressure
P=f/a
Si unit for pressure
N m -square
Hypothesis for pressure
The smaller the surface area, the larger the pressure
Assume that gas particles are represented by footballs and the wall of a container is represented by a wall.
When the footballs hit the wall, pressure will be exerted by the footballs on the wall. A similar situation occurs in the collision of gas particles with wall of a container that will produce gas pressure.
Factors that affects air pressure
Volume, Temperature
Volume ap
When the volume of air reduced, its air pressure will increase
Temperature ap
air pressure increases with the increase in its temperature.
Air pressure
Collisions between gas particles in the air and the wall of a container
Atmospheric pressure
collision of gas particles in the atmosphere with certain bodies.
Atmospheric pressure depends on
Height above sea level
Hypothesis for atmospheric pressure
Atmospheric pressure decreases as the height above sea level increases
Areas that has more gas particles
Near to sea level
Magdeburg hemispheres
When the air trapped in the hemispheres is pumped out, the space within the hemispheres forms a vacuum. On the outside of the hemispheres, the atmospheric pressure exerts a huge force on the outer surface of the hemispheres that keeps both hemispheres (tightly) together. Both hemispheres cannot be separated even by using a large force. The pressure inside the hemispheres becomes very low.
Drinking straw
When one end of the drinking straw is sucked, the air inside the drinking straw is removed.This action causes the air pressure in the drinking straw to decrease and become lower than atmospheric pressure.The higher atmospheric pressure on the surface of the liquid pushes the liquid into the drinking straw and then up into the mouth through the drinking straw.
Plunger
A plunger is pressed down to drive out the air underneath the rubber cup, X. The volume of air in X is reduced. As the plunger is pulled upwards, the volume of air in X increases while the air pressure in X becomes lower than air pressure in Y. The higher air pressure in the space Y in the drainage pipe will push and break up the blockage
Siphon
A siphon is a tube completely filled with liquid. When the liquid in a siphon flows out of its lower end, the pressure of the liquid at this lower end of the siphon is reduced. Atmospheric pressure on the surface of the liquid in the container in the higher position will push the liquid into the upper end of the siphon. As a result, this causes a continuous flow of liquid through the siphon from the upper end to the lower end.
Syringe
When piston is pulled upwards, the volume of air in the space below the piston increases while its air pressure decreases.The higher atmospheric pressure pushes the liquid up into the syringe through the hole of its needle.
Vacuum cleaner
When the electric fan is turned on and is rotating, some of the air in space X is sucked out through an opening. The reduced amount of air lowers the air pressure in space X. As a result, the outside air pressure which is higher causes air to be sucked into the vacuum cleaner.
Hypothesis for liquid pressure
Liquid pressure increases as the depth in a liquid increases
Effect is shown by for lp
volume of an air bubble which increases when its depth in water decreases
Design of a submarine
has a thick steel wall that can withstand the increase in water pressure in depths of water.
Thickness of walls of a dam
As water pressure increases with depth, a thicker wall is built at the base of a dam to withstand the higher water pressure
