Download Slide 1 - Planetscience

Terminal Velocity
Terminal Velocity
• When a sky diver leaves
the aircraft he speeds up
because there are
unbalanced forces acting.
His weight is greater than
the fictional drag force.
• As his speed increases,
the fictional drag due to
the air increases.
• Spreading himself like a
eagle increases the
surface area and
increases the fictional
drag
Velocity in a car
• When cars first set off they have
much more force accelerating
them than resistance slowing
them down.
• As the speed increases the
resistance builds up. This
gradually reduces the
acceleration until eventually the
resistance force is equal to the
drive force.
The Science Behind it
Triangle
F
M A
Fluid Friction
•
Fluid friction differs from contact friction because the amount of fluid friction depends on how fast the object is
moving through the fluid. The greater the speed, the greater the friction.
•
This can be felt if you are in a pool of water. Trying to walk from one side of the pool to the other is much
easier than trying to run. That's because the faster you move, the harder the fluid pushes against you.
•
When you examine contact friction you find that speed has no effect on the amount of kinetic friction.
Graphs
The red curve shows acceleration changing from large to small.
The blue line shows the cone's terminal velocity (constant velocity).