Terminal Velocity Flashcards
What types of friction are there?
Contact friction - the friction between two objects, solid surfaces.
Fluid friction - also drag/fluid resistance/air resistance. This is resistance by something which can flow like liquid or gas. The force depends on viscosity of the fluid, and increases as speed does. It depends on the shape/size of the object. A large object will have greater resistance force. Frictional forces always act opposite, never cause movement, and convert kinetic energy into heat.
How would terminal velocity be reached in a car? (refer to getrevising document to find graphs).
When driving, a driving force, which stays constant, is used to accelerate. As the speed increases, the resistance force will, and this reduces the resultant force on the car, reducing acceleration, until the resistance forces are equal to the driving force. The car continues at a constant velocity.
How would terminal velocity be reached and changed for a parachutist?
When a man falls from a parachute, the force acting is weight. He will accelerate until air resistance equals his weight, and will then travel at a terminal velocity. The velocity is too fast to land safely. Opening his parachute increases air resistance massively, causing him to decelerate. As he is slowed down, air resistance will fall to equal his weight, lowering the terminal velocity.
How could terminal velocity of a ball bearing be found with a glass tube and thick liquid?
The terminal velocity of a ball bearing can be found in viscous thick liquid using an experiment…
- Put elastic bands around the tube at fixed distances with a ruler.
- Drop a ball bearing into the tube containing thick liquid such as glycerol, and use a stopwatch to measure the time it takes to reach each band.
- Repeat this to reduce random error, a strong magnet can be used to remove it from the tube.
- Calculate times of travel between elastic bands and calculate an average for each readinf, using this and distance to find the average velocity.
- Find when the velocity becomes constant - this is terminal velocity.
For more accurate readings, paper cones and a light gate may be used.
How would experiment results be processed and what could be changed in the experiment for different results?
A graph of velocity against time can be drawn, with a curve, to calculate the terminal velocity. Force diagrams may be drawn, forces are equal when terminal velocity is reacged. To change the terminal velocity or time taken to reach it, factors can be changed: the liquid, (more viscous liquids have a lower terminal velocity due to greater drag), perhaps add water to wallpaper paste; change ball size; change shape to make it more/less streamlined; change the object mass while maintaining same size, (heavier objects have a faster terminal velocity as more drag is needed to balance the weight).
