forces and presure Flashcards
Contact force
A force that acts when an object is in contact with a surface, air, or water.
Friction
Force resisting movement because of contact between surfaces.
Air resistance
The force of an object moving through air causing it to slow down.
Gravity
A non-contact force acts between two masses.
Non-contact force
A magnetic, electrostatic, or gravitational force that acts between objects not in contact.
Interaction pairs
When two objects interact there is a force on each one that is the same size but in opposing directions.
Newtons
The unit of force, symbol N.
Deforms
When an object changes shape.
Compress
To squash an object into a small space.
Tension
A stretching force.
Weight
The force of the Earth on an object due to its mass.
Mass
Amount of stuff a thing is made of.
Balanced
Forces acting on object that are equal and in opposite directions.
Unbalanced
Opposing forces on an object that are unequal.
what is meant by forces always come in pairs
it means that no matter what forces always have an opotion but they may not always be equel for example thrust and frict
Atmosphere
The layers of gases that surround the Earth. The important gases in the atmosphere are nitrogen, oxygen and carbon dioxide.
Atmospheric pressure
The weight of air resting on the Earth’s surface.
Fluid
A substance that can flow, such as a liquid or a gas
Normal
Acting at an angle of 90° to a surface or boundary.
Pascal
Unit of pressure. Pascal (Pa), eg normal atmospheric pressure is 1.01x105 Pa.
Pressure
Force exerted over an area. The greater the pressure, the greater the force exerted over the same area.
surface area
The total area of an object, for example the area of a skydiver’s body facing the air as they fall, or the area of a car tyre that touches the road.
upthrust
Upwards force exerted by a liquid or gas on an object floating in it.
Pressure in gases
Gas pressure (air pressure) is when the air molecules collide into each other. Lots of collisions make a high gas pressure because there is a big force over a small area.
Pressure in liquids
Liquids are incompressible. This is because the particles are very close together and touching each other, so there is very little space between them. The water molecules are pushing on each other and on surfaces, and this liquid pressure acts in all directions.
Pressure on solids
When you stand on any surface you exert a force on it because of your weight. Your weight is spread out over the area of your foot. You are exerting a pressure on the ground.
Turning forces
Whenever you open a door you are using a turning force. A turning force acts in a certain distance from a pivot. The turning effect of a force is called a moment. The moment depends on the force being applied and how far it is from the pivot. Moment equals force multiplied by perpendicular distance from the pivot.
force
a push pull or twist that explains the way things move
mass and weight
Mass and weight are two different quantities. Mass is the amount of matter in an object and weight is the force experienced due to gravity. The unit of mass is kg and the unit of force is Newton. The unit of gravitational field strength ‘g’ is N/kg. Mass is always the same anywhere in the Universe but weight changes as ‘g’ changes.
how do things float
Liquids pass on any pressure applied to them. It is liquid pressure that produces upthrust, the force that keeps things afloat. If you push a balloon into a bucket of water you can feel the water pushing back. Upthrust acts on any object that is floating, or is submerged in a liquid.
what forces do magnets exert
magnetic forces without them touching
what is rubbing a balloon and picking up pieces of paper an example of
of electro static force
what is a field
the region around an object that experiences a force
what is gravitational field
where things with mass experience gravitational force
do forces get stronger or weaker the further away from the field
weaker
