forces Flashcards
What is a force?
A force is a push or a pull that acts on an object due to the interaction with another object.
What units are forces measured in?
Force is measured in newtons (N).
Two main categories of forces?
contact forces and non-contact forces.
What is a contact force?
A force that can cause or change motion of an object by touching it.
Four examples of contact force?
Friction, Normal/Reaction Force, Air Resistance, Applied Force.
What is a non-contact force?
Force that results when the two objects are not in physical contact with each other, yet are able to exert a push or pull.
Three example of non-contact force?
Gravitational Force, Electrical Force, Magnetic Force.
Tension
It is a pulling force exerted on an object by a string, rope, or rod.
Air resistance
It’s when an object moves through the air it experiences air resistance. This force acts against the direction of movement. The faster the object is traveling the greater the air resistance.
Electrostatic force
It is experienced by a charged particle in an electric field.
Upthrust
It is an upwards force that acts on an object when it is in a fluid
Friction
It’s when two objects slide past each other they experience friction. Friction is a force that acts between two touching surfaces and prevents or resists them moving against each other.
Normal reaction force
It’s when an object pushes on a surface like a table, wall, or the ground, the surface pushes back on the object with a balancing force. The normal reaction force always acts at right angles to the surface.
Thrust
It is a driving force exerted by an engine to make an object move.
Magnetic force
It’s is experienced by a magnet or a magnetic material, eg iron, when placed in a magnetic field. This force can pull the two objects together or push them apart.
How to measure a force?
A force meter, also known as a newton meter, can be used to measure the size of a force.
When forces act on objects what are the effects?
The object can speed up or slow down.
The object can change direction.
The shape of the object can change.
What is friction?
Friction is a contact force and acts against the movement of an object.
When is friction useful?
friction is why we do not slip when we walk along the pavement.
How to make a object move?
To make an object move, you must apply force to it. This motion force has to overcome the force of friction, otherwise it will not move.
What factors affect friction?
Materials, Weight, Surface area and Liquids.
How does Materials affect friction?
Some materials will create less friction due to their surface. A rough surface will create more friction than a smoother surface.
How does Weight affect friction?
Things that are heavy will be subject to more friction than things that are light.
How does Surface area affect friction?
If the area of the two objects rubbing together is large, it will create more friction.
How does Liquids affect friction?
The addition of a liquid can reduce friction by making the surface slippy. Dry surfaces tend to have more friction.
What are the two kinds of friction?
Air resistance and Water resistance
What are air and water resistance?
Air resistance is when a solid object moves through air or gasses.
Water resistance is when a solid object moves through water or liquids.
How can we use friction to our benefit?
Braking systems in vehicles
Stringed musical instruments
Door stops
Writing.
How does friction cause problems?
Friction makes movement harder.
Friction wastes energy.
Friction creates heat.
Friction wears things out.
What can we do to reduce friction?
Streamlining is where actions are taken to reduce the amount of friction allowing things to move more easily.
What is Gravity?
Gravity is a force exerted by one object on another when they are near each other.
What affects gravity?
Gravity is affected by the mass and the proximity of the objects.
What is the earth’s gravitational force per kilogram?
The Earth has a gravitational field strength of 10 newtons per kilogram (N/kg).
Why don’t we feel the earth’s gravitational field?
The Earth’s gravitational field strength is larger than our own, so we don’t notice the gravitational force that our own bodies exert.
What is mass?
Mass is the amount of matter (stuff) an object is made up of.
What unit is used for mass?
The unit of mass is kilograms (kg).
Does the value of mass change in different locations?
The value does not change when an object’s location changes.
What is weight?
The total amount of force acting on an object due to gravity.
What unit is used for weight?
Measured in newtons (N).
Does the value of weight change in different locations?
The value does change when an object’s location changes.
How to calculate weight
Weight = mass × gravitational field strength
What is Time?
It is how long something takes to happen. This can also be called the duration of an event or journey.
What is Speed?
It is how fast or slow something travels.
What is Distance?
It is how far something travels.
What is the equation for time?
Time = Distance / Speed
What is the equation for speed?
Speed = Distance / Time
What is the equation for distance?
Distance = Time X Speed
A car travels at a speed of 70 km/h. How far will it travel in 3 hours?
D = T x S
3 x 70 = 210 km
I walked 16 km in 4 hours, what speed was I walking at?
S = D / T
16 / 4 = 4 km/h
I walked 20 km at a speed of 4km/h. How long did it take me?
T = D / S
20 / 4 = 5 km/h
