LEARN! Flashcards
How do brakes slow an object down
Apply friction
Transfers kinetic energy from the car into other forms
How does rain effect stopping distances
Reduces friction
How do you know ifs wave is longitudinal
It will have compressions and rarefractions
Transverse waves
The oscillations are PERPENDICULAR to the direction of energy transfer
Longitudinal waves
The oscillations are PARALLEL to the direction of energy transfer
Example of a transverse wave
EM waves
A ripple
Example of a longitudinal wave
Sound
Ultrasound
Shock waves
What is the amplitude of a wave
Distance from rest to crest
What is the normal
Imaginary line that is perpendicular to the surface
What is diffraction
When waves spread out after passing through a small gap
Why do rays get refracted
Ray hits a material with a different density
So speed will change
Describe how electromagnetic radiation is used in security marking
U-V radiation is absorbed by certain chemicals with fluorescent properties
What is a resultant force?
A single force which has the same effect as all the forces acting together
Why is a 13A fuse too big for 3.7A
Will allow too great a current through and not provide protection
Why is a switch not closed all the time
Current flowing through a resistor will warm it up so the resistance of the resistor will change
How do airbags reduce force acting on a driver
- increases time taken for the force to act
- momentum changes slowly
- decreases forces acting on driver
How does the speed of a truck effect the size of resistant forces it experiences
As speed increases, resultant force increases
Why do falling objects reach terminal velocity
- resistive forces act
- these increase as the object accelerates
- eventually these will balance and the object will reach terminal velocity
How do parachutes decrease a skydivers terminal velocity
- increases air resistance
- forces acting are balanced at a lower speed therefore terminal velocity is lower
What is a reaction time
Time it takes you to react from an event
Describe the differences between a scalar and a vector quantity
Scalar quantities have magnitude
Vector quantities have both direction and magnitude
On a distance time graph what is a steady speed shown by
Straight line
If an object travels at a steady speed is there a resultant force
No
Two factors that effect a reaction time
Drugs
Alcohol
Weather
What will happen if you increase the cars maximum breaking force
It will decrease the braking distance
Why is fruit sterilised with a gamma ray
Treating fruit with radiation kills bacteria
This means the fruit will stay fresh for longer
Why can x-rays be used to treat cancer
They are ionising
So kill cancer cells
Why does something echo in a hall but not in a field
The sound is refracted off the walls of the hall and there are no walls outside
