PAG 1.2 - Investigating Terminal Velocity Flashcards
What safety precautions should be taken when carrying out this experiment?
Spillages must be cleaned up immediately, as spills can lead to a risk of slipping and injury
Suggest why light gates shouldn’t be used when carrying out this experiment
Light gates rely on clear breakage of the beam, this will not occur in this experiment, since it is unlikely that the ball will cut the beam, may also be disturbed by the coloured liquid
What forces act on the ball as it sinks down a tube of liquid?
A downwards force of weight, and two upwards forces of drag and up thrust
Describe the forces on the ball when it reaches terminal velocity?
At terminal velocity, the downwards forces on the ball will equal the upwards forces
Weight = upthrust + drag
Describe how you should take time readings in this experiment
Time readings should be taken at eye level to the rubber bands
The lap function should be used to record the time of each rubber band
How can you ensure that the time readings are accurate?
Same person record the time readings throughout.
They should measure at eye level to the rubber bands and must ensue they stop the timer at the same relative position between the ball and the band each time
Suggest why it may be advantageous to use a steel ball
Steel ball bearings are magnetic and can be sued to easily lift the ball from the bottom after each run
How should the bands be positioned on the tube?
Each pair of bands should be positioned sufficiently apart so that the time intervals between each are easily observable and measurable
How can the density of the liquid in the measuring cylinder be determined?
Use a mass balance to measure the mass of the empty cylinder, add the liquid and subtract the old value from the new value.
Divide this by the volume of the liquid
How can the average speed in each interval be calculated?
Measure the distance between the two bands that make up the interval.
Divide this by the time taken for the ball to travel between two bands
How can the terminal velocity be obtained from a velocity-time graph?
When at terminal velocity, the graph should level off, add this velocity will be the terminal velocity
How should you plot the data you obtain?
Plotted on a velocity against cumulative time graph, results in a smooth curve
How is displacement determined from a velocity-time graph?
Area under the graph
How can the radius of the small ball be measured?
A screw gauge micrometer can be used to measure the diameter of the ball, and can be halved to get the radius/
OPTIONAL:
What equation can be used to determine the viscosity of the liquid?
(Mg - 4/3 r3 g p) / 6 x pi x r x v
