P5 - Terminal Velocity Flashcards
What does friction do?
Makes objects slow down
What always happens if an object has no force propelling it?
It will always slow down and stop because of friction (unless you’re in space where there’s nothing to rub against)
What direction does friction always act opposite to?
The direction of movement
What do you need to have to travel at a steady speed?
The driving force meeds to balance the frictional forces
When do you get friction?
You get friction between two surfaces in contact, or when an object passes through a fluid (drag)
How can you reduce friction?
By using a lubricant
When does drag increase?
When speed increases
What is drag?
Drag is the resistance you get in a fluid (a gas or a liquid)
(Air resistance is a type of drag)
What is the most important factor to reducing drag?
Keeping the shape of the object streamlined
( This is where the object is designed to allow fluid to flow easily across it, reducing drag.
Parachutes work in the opposite way - they want as much drag as they can get )
What do frictional forces from fluids always increase with and why?
Frictional forces from fluids always increase with speed. A car has much more friction to work against when travelling at 70 mph compared to 30 mph. So at 70 mph the engine has to work much harder just to maintain a steady speed
What do objects falling through fluids reach?
Terminal velocity
Why does a falling object when it first sets off accelerate?
As the force of gravity is much more than the frictional force slowing it down
When speed increases what also increases?
Friction builds up
When friction builds up when falling what does it reduce?
This gradually reduces the acceleration until eventually the frictional force is equal to the accelerating force (so the resultant force is zero).
This then means it will have reached its maximum speed or terminal velocity and will fall at a steady speed.
What does terminal velocity depend on?
The shape and area of an object
When do objects have lower terminal velocities?
The less streamlined an object is and when an object has a large surface area
( This means if you dropped a marble and a beach ball off a tall building, the marble’s terminal velooity would be higher than the terminal velocity of the beach ball . This is because there is more air resistance acting on the beach ball, at any given speed. So the beach ball spends less time accelerating (and so doesn’t speed up as much) before the air resistance is large enough to equal the accelerating force )
