physics mocks: Flashcards
speed:
->the distance travelled per unit time
-if something is changing, it’s accelerating (near the Earth it is constant)
average speed = total distance/total time
s (m/s) = d (m) /t (s)
velocity:
->speed in a given direction
acceleration:
->change in velocity per unit time
acceleration = change in velocity/time taken
a (m/s^2)= v (m/s) -u/t (s)
equation for the final speed:
(final speed)^2 = (initial speed)^2 + (2 x acceleration x distance)
v^2 = u^2 +2as
distance-time graphs:
-the gradient is velocity
-negative gradient = returning back to the starting point
-a horizontal line = stationary
-if the distance = 0, it is back at the starting point
-curved line = velocity is changing, and it is accelerating
velocity time-graphs:
-the gradient is acceleration
-negative gradient = deceleration
-if speed = 0, it is at rest
-horizontal line = constant speed
-area under the line = distance travelled
-curved line = acceleration is changing
vectors:
have magnitude and direction
scalars:
have just magnitude
examples of scalar quantities:
distance, speed, time, energy…
examples of vector quantities:
displacement, velocity, acceleration, force
effects of forces:
-forces can change the speed, shape or direction of a body (measures in newtons (N))
eg: gravitational, electrostatic
friction:
forces between two surfaces which impedes motion and results in heating
eg: air resistance is a form of friction
how to find the resultant force:
-add together if in the same direction
-subtracted if in the opposite direction
Newton’s first law:
states that an object has a constant velocity unless acted on by a resultant force
Newton’s second law:
force = mass x acceleration
f=ma
mass & weight:
-measure of how much matter is in an object, measured in kg
-weight is a gravitational force
weight = mass x gravitational field strength
W = mg
-gfs on Earth is 9.8N/kg
terminal velocity:
-initially, there is no air resistance and the only force acting on it is weight
-as it falls, it accelerates which increases its speed and hence air resistance
-this causes the resultant force downwards to decrease
-therefore, the acceleration decreases
-eventually they are equal, opposite and balance so there is no resultant force
-so, there is no acceleration and the terminal velocity is reached
deformation:
-elastic deformation is when the object returns to its original shape when the load has been removed
eg: a spring being stretched
Hooke’s Law:
states that for a spring, F = kx where F is the force applied to the spring, k is the spring constant, and x is the extension
what does Linear and Non-Linear represent in a Hooke’s Law diagram?
linear (straight line) force extension graph: -Elastic deformation following Hooke’s law:
-the point it stops being linera is called the limit of proportionality. From then on, it does not obey Hooke’s Law, and gradient becomes k
non Linear (curved line) force extension graph:
-deformation not following Hooke’s Law
-after this region, it will fracture
general waves properties:
-transfer energy and information without transferring matter
-the particles oscillate (vibrate) about a fixed point
transverse waves:
-have peaks and troughs
-vibrations are perpendicular to the direction of travel
-eg: light
longitudinal waves:
-consists of compressions (particles pushed together) and rarefractions (particles moved apart)
-vibrations are in the same direction as the direction of travel
-eg: sound
amplitude:
the distance from the equilibrium position to the maximum displacement