1 Motion Flashcards
Average speed equation
Average speed = total distance / total time
Average acceleration equation
Average acceleration = change in velocity / time taken
a = (v - u) / t
On a distance-time graph, the gradient of the line is numerically equal to …
the speed
On a speed-time graph, the gradient of the line is numerically equal to …
the acceleration
On a speed-time graph, the area under the line is numerically equal to …
the distance traveled
Velocity vs. Speed
Speed is the rate of distance covered. It is scalar.
Velocity is speed in a particular direction. It is vector.
If no external force is acting on it, an object will … (2)
If stationary, remain stationary
If moving, keep moving at a steady speed in a straight line
Speed-time graph for an object at rest
Line at zero, along the x-axis (y-axis is speed)
Speed-time graph for an object with a constant speed
Horizontal line (y-axis is speed)
Speed-time graph for an object with changing speed
A line that moves up or down (y-axis is speed)
A micrometer screw gauge is used to measure …
very small distances
Vector quantities
Magnitude and direction are both required to define the quantity
Scalar quantities
Quantities that can be defined with magnitudes only
Retardation
Deceleration: it is negative acceleration, or slowing down
Displacement vs Distance
Displacement is distance in a single direction. It is vector.
Distance is the path taken irrespective of the direction. It is scalar.
The acceleration of free fall (g) near to the Earth is …
constant
Force
a push or a pull, exerted by one object on another: it has direction as well as magnitude, so it is a vector
Force SI units
Newtons (N)
Mass SI units
Kilograms (kg)
Acceleration SI units
Metres per second squared (m/s²)
Inertia
Resistance to change in velocity
More mass –> more inertia
Unbalanced forces are equivalent to a single force, called the …
resultant force
Define the newton (1 newton is equal to …)
1 newton is the force required to give a mass of 1 kilogram an acceleration of 1 metre per second squared
Static friction vs Dynamic friction
Static friction > Dynamic friction
Starting friction > Moving friction
Gravitational force main features (3)
All masses attract each other
The greater the masses, the stronger the force
The closer the masses, the stronger the force
Weight equation
Weight = mass x gravity
W = mg
To every action there is an …
equal but opposite reaction
Vectors and the parallelogram rule (3 steps)
- From 0, draw two lines to represent the vectors: the direction and length of each line must be in proportion to the magnitude of each
- Draw in 2 more lines to complete the parallelogram
- Draw in the diagonal from 0: it represents the resultant magnitude and direction
Centripetal force
the inward force needed to make an object move in a circle
More centripetal force is needed if … (3)
the mass of the object is increased
the speed of the object is increased
the radius of the circle is reduced
Mass vs Weight
Mass is the quantity of matter in a substance
Weight is the force exerted on an object in a gravitational field due to its mass
The Earth is the source of a …
gravitational field
Gravitational force SI unit
N / kg
Density equation
density = mass / volume
p = m / V
Forces may change the ____, _____ and ______ of a body
size, shape, motion
Hooke’s law
If the extension is proportional to the load beneath its elastic limit, an object obeys Hooke’s law
Equation involving spring constant
load = spring constant x extension
F = kx
Friction
the force between two surfaces which impedes motion and results in heating
Air resistance is a form of …
friction
Resultant force of scalar quantities calculated by …
addition (and/or subtraction)
If there is no resultant force on a body, it either …
remains at rest or continues at a constant speed in a straight line
Pressure equation
Pressure = force / area
p = F / A
Moment of a force
a measure of its turning effect
Moment equation
Moment = product force x perpendicular distance from the pivot
Principle of moments: if an object is in equilibrium …
the sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about that point
When there is no resultant force and no resultant turning effect, a system is in …
equilibrium
