P10 Force and Motion P14 Light Flashcards
Resultant Force Equation:
Mass x acceleration
Newton’s second law of motion
States that acceleration of an object is proportional to the resultant force of the object
States that acceleration of an object is inversely proportional to the mass of the object
What is the inertia of an object
It’s tendency to stay at rest or in uniform motion
What’s the weight of an object
The force acting on the object due to gravity. It’s mass is the quantity of matter in the object
At what speed of an object active only by gravity accelerate at
10 mph squared
Terminal velocity
The terminal velocity of an object is the velocity it eventually reaches when it is falling. The weight of the object is that equal to the frictional force on the object
What is the resultant force on an object moving at its terminal velocity
Zero
What does the stopping distance depend on
The braking distance and the thinking distance
What is opposes the driving force of the vehicle
Friction and air resistance
Thinking distance
The distance travelled by the vehicle in the time it takes the driver to react (reaction time)
Stopping distance
This is the shortest distance of the vehicle can safely stop in
Breaking distance
The distance travelled by the vehicle during the time the braking force acts
Equation for stopping distance
Thinking distance + braking distance
What sort of factors increase braking distance
High-speed, poor weather conditions and poor vehicle maintenance
What sort of factors increase thinking distance
Poor reaction time due to tiredness alcohol drugs or using a mobile phone and high-speed both increase the thinking distance
Equation for breaking force of the vehicle
F= m x a
Equation for momentum
p = m x v
Momentum units
kg m/s
Momentum is an example of what
A vector quantity
What is a close system in the context of momentum
A system in which the total momentum before an event is the same as the total amount momentum after the event. This is called conservation of momentum
What happens when two objects push each other apart
They move a different speeds if they have unequal masses and with equal and opposite momentum so the total momentum is zero
Equation for momentum, when two objects recoil from each other
m1 v1 + m2 v2 = 0
What does the force of the impact depend on when vehicles collide
On the mass, change of velocity and the length of the impact time
How does impact time affect the impact force
The longer the impact time the more the impact forces reduce
What happens when two vehicles collide
They exert equal and opposite forces on each other
The total momentum is unchanged
Impact force equation
Impact force = change of momentum / impact time
So the short the impact on the greater impact force
How do you cycle helmet and cushioned surfaces, for example in playground, help to reduce the impact forces
By increasing the impact time
How do you seatbelt and airbag help to decrease the impact forces
By spreading the force across the chest and increasing the impact time
What can conservation of momentum be used for, after car experiences impact
The speed of the car
Why are side impact bars and crumble zones installed
To give way in an impact and so increase the impact time
When with an object by classified as elastic
If you’re returned to its original shape after removing the force deforming it
What is the extension of an elastic object
The difference between the length of the object and its original length
What is the extension of the spring is directly proportional to
To the force applied to it as long as the limit of proportionality is not exceeded, this relationship is linear
What happens beyond the limit of proportionality in an elastic object
The extension of the spring is no longer proportional to the applied force, this relationship becomes non-linear
What is the normal at a point on a mirror
A line drawn perpendicular to the mirror
The law of reflection states:
The angle of incidence is equal to the angle of reflection
For a light ray reflected by a plane mirror what is the angle of incidence and the angle of reflection?
The angle of incidence and the angle between the incident ray and the normal
The angle for flexion is the angle between the reflected ray and the normal
Specular reflection
His reflection in a single direction without scattering
Diffuse reflection
It’s reflection from a rough surface that scatters the light
Refraction
Is the changing direction of the waves when they travel across a boundary from one medium to another (different densities)
What happens when the light ray Travels from air to glass
The light grey with cracks as it covers from air into glass, the angle of refraction is less than the angle of incidence
What happens on the light rail travels from glass into air
As it travels from glass into at the angle of a fraction is more than the angle of incidence
How does the wavelength of light differ when you move from Violet to read across the visible spectrum
The wavelength increases
What does the colour of the surface depend on
On the pigments of the surface materials and the wavelength of light that pigments absorb
A translucent object…
Let’s light passes through it but scatters or reflects the light inside it
A transparent object…
Let’s all the light that enters it pastorate and does not start or affect the lights inside the object
What do you convex lenses do
Focuses parallel rays to a point called the principal focus (by coverging them)
What are examples of where convex lenses are used
A converging lens is used as a magnifying glass and in a camera to form a clear image of a distant object
What do you concave lenses do
Makes parallel rays spread out as if they had come from a point called the principal focus
Find me a diverging lens be used
To correct short sight
What is the focal length
The distance from the centre of the lens to the principal focus
When is a real image formed
I real image is formed by a convex lens if the object is further away than the principal focus
When is it a virtual image formed
A virtual image is formed by a convex lens if the object is nearer than the principal focus
Equation for magnification
Magnification= image height / object height
What happens to an object when it is placed between a convex lens and its principal focus
The image formed is virtual upright magnified and on the same side of the lens as the object
What is the convex lens in a camera used for
To form a real image of an object
What is the convex lens in a magnifying glass form
It forms a virtual image of an object
