Physics Flashcards
What is displacement?
Displacement is a distance in a given direction.
What is a vector quantity?
A vector quantity is a physical quantity which has magnitude and a direction.
What is a scalar quantity?
A scalar quantity has a magnitude but no direction.
How can a vector quantity be represented?
by an arrow in the direction of the vector and of length in proportion to the magnitude of the vector
Name 3 things forces can change in relation to the object.
Forces can change the shape of an object, or change its motion or its state of rest
What is the unit of force?
Newtons (N)
What is a contact force?
A force that acts on objects only when the objects touch each other.
What happens when two object interact?
They always exert equal and opposite forces on each other.
What is the resultant force?
A single force that has the same effect as all the forces acting on an object.
What is always true if the resultant force on an object is zero?
The object stays at rest or at the same speed or direction.
What is always true if the resultant force on an object is greater than zero?
The speed or direction of the object will change
If two forces act on an object along the same line, what is the resultant force?
Their sum, if the forces act in the same direction or their difference, if the forces act in opposite directions
What is the centre of mass of an object?
The point where its mass can be thought of as being concentrated.
Where is the centre of mass of a uniform ruler?
At its midpoint
When an object is freely suspended, where does it come to rest?
With its centre of mass directly underneath the point of suspension
Where is the centre of mass of a symmetrical object?
Along the axis of symmetry
How can waves be used?
Waves can be used to transfer energy and information
Describe Transverse waves.
Transverse waves oscillate perpendicular to the direction of energy transfer of the waves. Ripples on the surface of water are transverse waves. So are all electromagnetic waves.
Describe longitudinal waves.
Longitudinal waves oscillate parallel to the direction of energy transfer of the waves. Sound waves in air are longitudinal waves.
What do Mechanical waves need and are they transverse or longitudinal waves?
Mechanical waves need a medium (a substance) to travel through. They can be longitudinal or transverse waves
What does a radio active substance contain?
Unstable nuclei that become stable by emitting radiation
What are the three main types of radiation?
Alpha (α)
Betta (β)
Gamma (γ)
What is radioactive decay?
process where an unstable atomic nucleus loses energy by emitting radiation
Can you predict radioactive decay?
No, it’s a random event
What did Rutherford use alpha particles for? And what does this mean he found?
He used alpha particles to probe inside atoms.
He found that some alpha particles were scattered through large angles
What could Rutherford’s plum pudding model not explain? And which model could explain it?
The plum pudding model couldn’t explain why some alpha particles were scattered through large angles. Later, the nuclear model explained this.
Where is most of an atom’s mass located?
In it’s small positively charged nucleus
List the electromagnetic spectrum (largest-smallest)
radio waves microwaves infrared radiation visible light ultra violet light x-rays gamma rays
What can the human eye see? (and what is it’s range?)
Can inly detect visible light.
Ranges from 400nm to above 700nm
wave speed (m/s) =
frequency (Hz) x wavelength (m)
What does white light contain?
All the colours of the visible light spectrum,ranging from red to violet.
What is infrared radiation used for?
Carrying signals from remote control handsets and inside optical fibres.
What are microwaves used for?
To carry satellite TV programs and mobile phone calls.
What type of electromagnetic radiations are hazardous and in what way?
Microwaves and radio waves- can heat internal parts of human bodies
Infrared radiation- can cause skin burns.
What does the wavelength in radio waves affect?
- how far they can travel
- how much they spread
- how much information it can carry
What can infrared radiation be used for?
all of their uses are related to heat, like:
- infrared cameras
- cooking
- electric heaters
What are optical fibres?
Very thin transparent fibres that are used to transmit fibres that are used to transmit communication signals by light and infrared radiation. Pulses of visible light are used as when the light hit the walls of the fibres, it’s reflected back into the fibre, so that it bounces back and fourth until it reaches the end,
What is ionising radiation?
Radiation with enough energy to knock electrons of atoms.
What are the three examples of ionising radiation?
Ultra violet
X-rays
Gamma rays
What dangers can ionising radiation have?
Can cause gene mutations
UV can cause tanning/burning which can lead to skin cancer
What are the uses of ionising radiations?
UV -tanning lamps, security ink, energy efficient lamps
X-rays -medical imaging, medical treatment
Gamma rays -medical treatment
How do x-ray images work?
The x-rays are absorbed more by bones and teeth (making the image whiter) but x-rays pass through tissues) making them black.
