Phy2.1-2.6 Flashcards
Force is a – that can change the — of an object.
push; pull; direction, speed, size, and shape
Prediction (–): sth that you –
Hypothesis (–) : a –/ explanation made on the — that can be –
You make a - based on the -.
猜测 think would happen in the future
假设 scientific theory; basis of evidence; further tested
prediction; hypothesis
Newton’s Laws:
1. An object will — (rest will rest, move will move), unless —.
2. F=–
3. When there is an action force, there is always an —.
remain at what it is doing already;
acted on by an unbalanced force
ma (力量会被质量和速度影响）
equal and opposite reaction force
Non-contact forces:
-,-,-
1. Act between any object that has - (force=-). Acts toward the –.
2. (静电力) Act between objects that are –. (can -/- other - objects)
3. （磁力）Act between magnets, and between magnets and magnetic materials such as -,-,/-.
Gravitational forces; Electrostatic forces; Magnetic forces
mass; weight; centre of the Earth
electrically charged; repel; attract; charged
iron; steel; nickel
Contact forces:
-,-,- (types of drag),-,-,-,-
1. 摩擦力 Acts when – are in contact. (to stop objects moving)
2. 水阻&风阻 Act on objects moving through -&-. (collisions slow objects down)
3. 冲力Pushes —.
4. 浮力 Upward force on an object that is in contact with -/-
5. 拉力 Acts when objects are -
6. Pushes you - in reaction to your —. (=normal force)
friction; air&water resistance; thrust; upthrust; tension; reaction;solid surfaces
air; water
a car/ plane forwards
a fluid/ air
pulled
up; weight pushing sth downwards
You can measure the - of a -. Forces are measured in units called - (-). A device for measuring forces is called a - (aka-; ex. -)
size; force; newtons; N; forcemeter; newtonmeters; spring balance
The forces that slow down objects that are moving on solid ground are -/-.
The forces of - & - will act on anything falling through the air.
A force called - acts on any object that is - on water/- in water.
friction; air resistance
air resistance; gravity
upthrust; floating; submerged
scalar=-
vector (aka-) =-&-
only value
velocity; value; direction
-: the force of attraction between —.
(Pulling you down towards —)
gravity; all objects that have mass; the centre of the Earth
The - of the force of gravity between 2 objects depends on:
1. - of the 2 objects
(the bigger the -, the bigger the force of —)
2. how – they are
size; mass; gravity is needed to pull it down; far apart
The force of gravity — on Earth is called –. The force of gravity is - on different planets. The – the planet, the larger the force of gravity.
acting on an object; its weight; different; more massive
Weight=-; measured in -
Mass=–; measured in -.
a force; newtons (N); the amount of matter in an object; kilograms (kg)
There is a gravitational field(重力场) —. This is a region where —.
around all objects; a mass experiences a force
Gravitational field strength:
Earth: - N/kg
Moon: - N/kg
10(9.81); 1.6
weight=- x — (-/-)
mass; gravitational field strength (N/kg)
Scientists ask - about the world around them. They make - and use the - from their - to come up with an -. They make - and use them to develop -.
questions; observation; evidence; observations; explanation; observations; ideas
A moving object would only – if a force acted on it.
change direction
proof= –/-
evidence=–
It is possible to prove that a scientific explanation is true. T/F
Newton’s law of gravitation was used to —.
If new evidence does not support an explanation, then scientists
look for a new -.
can be right/wrong
must be right
F (already considered as true)
send people to the Moon
proof
Scientists use the gravitational forces of the Sun and planets to —.
sent satellites into space
Air resistance depends — & —.
It - things -.
1. Objects moving with — will push more air out of the way & —.
(Why the faster you are, the greater the air resistance?)
2. Air resistance is less if the —.
on the speed of the object; its area in contact with the air
slows; down
a higher speed; experience more air resistance
(This is because according to N3: When there is an action force, there is always an equal & opposite reaction force. 反作用力)
area in contact with the air is small.
An object moving through the air — in the air. These — provide the resistance.
collides with the particles ; collisions with air particles
The shape of – reduces air/ water resistance.
streamlined objects (streamlining=流线型)
arrow up: -
and
arrow down:-
arrow left:- and arrow right:-
air resistance; gravity
air resistance; thrust/drive/ action force
Usage of air resistance:
Slows -,-&-
Rocket cars —
aircrafts(flaps), cars, parachutists
use parachutes to brake
