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kinematics: describing motion, which is, consist of, which are, which is,…
kinematics: describing motion
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speed
the distance an object travels per unit of time, showing how fast it moves without considering direction.
average speed
total distance travelled divided by the total time taken.
instantaneous speed
the speed of an object at a specific moment in time.
units
standard quantities used to measure physical things, so everyone understands the same value.
determining speed
measuring the time it takes to travel between two fixed points.
distance and displacement, scalar and vector
distance
total length an object travels, without considering direction, and is a scalar quantity.
displacement
the straight-line change in position of an object from its starting point to its ending point, including direction.
vector quantity
a measurement that has both magnitude and direction, such as displacement, velocity, or force.
scalar quantity
a measurement that has only magnitude and no direction, such as speed, distance, mass, or time.
speed and velocity
velocity
the rate of change of displacement in a specific direction (speed with direction).
speed and velocity calculations
Speed is total distance divided by time, while velocity is displacement divided by time with direction.
how to make the most of units
always write them clearly, use the correct SI units (like m, s, kg), and convert any given values to the same units before calculating
displacement-time graphs
a graph that shows how an object’s displacement changes with time, where the slope (gradient) of the line gives the object’s velocity.
deducing velocity from a displacement-time graph
Velocity is the slope of the displacement–time graph (change in displacement ÷ change in time).
combining displacement
vector addition, meaning each displacement is represented with its magnitude and direction, arranged head-to-tail, and the resultant vector is drawn from the starting point to the final position.
vector triangle
a triangle diagram used to find the resultant by adding two vectors head-to-tail.
resultant
a single vector that represents the combined effect of two or more vectors.
combining velocities
adding them together, if they go the same way add them, if opposite subtract them, and if at an angle, use the pythagoras to find the single total velocity.
subtracting vectors
adding the opposite of the second vector which first, take the vector you want to subtract, then reverse its direction, then add it to the first vector using normal vector-addition rules.
other examples of scalar and vector quantities
scalar
only have magnitude
mass, time, temperature, energy, speed, distance.
vector
have magnitude and direction
force, velocity, displacement, acceleration, momentum.
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