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Physics chapter 2: Kinematics - Coggle Diagram
Physics chapter 2: Kinematics
distance
the total length covered by a moving object regardless of direction of motion
measured in metres(m), it is a scalar quantity. the distance from A to B is the green path of 10 km and a blue path of 7 km, the total distance from A to B and back to A is either 20km, 17km or 14km
acceleration
the rate of change of velocity
achieved by taking the final velocity and subtracting off the initial velocity and taking that number and dividing it by the time taken
if the velocity is constant, or if the object is zero (the displacement is zero), the acceleration would be zero, zero acceleration does not necessarily mean the object is not moving
if the velocity is negative, the object is slowing down or the object starts travelling in the opposite direction (the displacement is negative), when this happens, the object is decclerating. To find the object's deceleration, apply the acceleration formula first before concluding its deccleration
if the velocity is positive, the velocity of an object is increasing
speed
it is the distance moved per unit time
measured in metre per second (m/s), it is a scalar quantity and is calculated by distance dividing by the time taken, so the cyclist's speed would be 300m/120s = 2.5m/s
average speed is the total distance travelled divided by the total time taken, this includes the total time taken includes wait time and stop time, also measured in metre per second(m/s)
displacement
the distance measured in the straight line between any two points in a specified direction
measured in metres(m), it is a vector quantity unlike distance. while there are 3 possible distances from point A to point B, the displacement from A to B is 5km due east of A, the displacement from A to B and back to A again is 0 as the person would be right back from the place he started
in this example, there are 2 routes from A to B
velocity
it is the rate of change of displacement
measured in metre per second (m/s) as well, it is a vector quantity and is calculated by displacement divided by the time taken, so the cyclist's displacement would be 168m/120s = 1.4m/s
average velocity is taking the total displacement divided by the total time taken, includes break, wait and stop time, also measured in metre per second(m/s)
in this example, a cyclist takes 120s to travel the distance of 300m from P to Q, the displacement is 168m
Displacement-time graphs
the gradient of the displacement-time graph tells the velocity of the object
velocity-time graphs
the gradient of the velocity-time graph gives the acceleration of an object, the area under the velocity-time graph gives the displacement of the object
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acceleration due to free fall
the acceleration of free fall for a body near the earth is constant, it is also known as the acceleration due to gravity where g=9.81m/s2
free fall only happens when there is no air resistance in a vacuum in which the only force acting on the abject is its own weight, the direction of the force is downwards towards the Earth
an object experiences constant increase in velocity under Earth's gravitational pull acceleration due to gravity is constant, acceleration is not dependent on the mass or size of the object
air resistance is a type of frictional force due to the object moving through the atmosphere and it always opposes the motion of the object. Air resistance increases with the speed, surface area of the object, and the density of air
