forces, acceleration, newtons law Flashcards
what happens at terminal velocity and why does it happen
the object moves at a steady speed in a constant direction because the resultant force acting on it is zero
what happens at the start when an object starts to fall
at the start, the object accelerates downwards due to the force of gravity
second stage of an object falling
as the object’s speed increases, frictional forces such as air resistance or drag increase
third stage of an object falling
at terminal velocity, the weight of the object due to gravity is balanced by the frictional forces, and the resultant force is zero
Between A and B (terminal velocity graph)
The object accelerates at first because of the force of gravity. Its speed increases. The resultant force acts downwards because the frictional force acting against it is less than the weight of the object.
Between B and C ( terminal velocity graph )
The object is still accelerating but its acceleration decreases as time goes by. Its speed still increases but by a smaller amount. The resultant force still acts downwards but is decreasing. This is because the frictional force acting against it is increasing as the speed increases, but is still less than the weight of the object.
between C and D ( terminal velocity graph
The object is not accelerating any more. It has reached its terminal velocity and is falling at a steady speed. The resultant force is zero because the frictional force acting against it is now the same as the weight of the object.
The object does not stop falling once its resultant force is zero, unless it has hit the ground.
what is Newtons first law
an object remains in the same state of motion unless a resultant force acts on it
what is inertia
The tendency of an object to continue in its current state (at rest or in uniform motion
what is Newtons second law
resultant force = mass × acceleration (m/s^2)
acceleration relationship to mass
inversely proportional
acceleration relationship to resultant force
proportional
what is inertial mass
The ratio of force over acceleration
what is Newtons third law
whenever two objects interact, they exert equal and opposite forces on each other.
often worded as ‘every action has an equal and opposite reaction’
examples of newtons third law
pushing a pram
the person pushes the pram forwards
the pram pushes the person backwards
a tyre on the road - the tyre pushes the road backwards
the road pushes the tyre forwards
