PAG 01.2 Investigating Terminal Velocity Flashcards
What safety precautions should be taken when carrying out this experiment?
If any spillages occur, they must be cleaned up immediately. Washing up liquid is very slippery and so spillages 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 a clear breakage of the beam. This will not occur in this experiment since it is unlikely that the ball will cut the beam. The line of the beam may also be disturbed by the coloured liquid
What forces act on a ball as it sinks down a tube of liquid?
A downwards force of weight, and two upwards forces of drag and upthrust
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 at each band
How can you unsure that the time readings are accurate?
The same person should record the time readings throughout. They should measure at eye level to the rubber bands and must ensure 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 bearing in this experiment
Steel ball bearings are magnetic. This ,Evan sure that a magnet can be used to easily lift the ball from the bottom of the liquid after each run
How should the bands be positions on the tube?
Each pair of bands should be positioned sufficiently far 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 first mass measurement from the new mass to obtain the mass of the liquid. Divide this by the volume of liquid to obtain density
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 the two bands
How can the terminal velocity be obtained from a velocity time graph?
When the ball reaches terminal velocity, the vt graph should level off. The velocity at which it levels off at is the terminal velocity
How should you plot the data you obtain on a graph?
The data should be plotted on a velocity against cumulative time graph. This should result in a smooth curve
How can the displacement of the ball be determined from a velocity time graph?
The area under the vt graph
How can the radius of a small ball be measured?
A screw gauge micrometer or a vernier calliper can be used to measure the diameter of the ball. This can then be halved to give the radius
