PAG 1.2 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 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
The downwards force on the ball will equal the upwards forces
Weight=upthrust and drag
Describe how you should take time readings in this experiment
At eye level to the rubber bands. The lap function should be used to record the time at each band
How can you ensure that the time readings are accurate?
The same person should record the time readings throughout. Measure at eye level to the rubber bands and ensure they stop the timer at the same relative position between the ball and band each time
Suggest why it may be advantageous to use a steel ball bearing in this experiment
Steel ball bearings are magnetic
This means 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 positioned on the tube?
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 liquid and subtract first mass measurement from the new mass to obtain mass of liquid
Divide this by volume of liquid to obtain density
How can average speed in each interval be calculated?
Measure distance between the two bands that make up the interval. Divide this by time taken for the ball to travel between the two bands.
How can the terminal velocity be obtained from a vt graph?
The vt graph should level off. This is at terminal velocity
How should you plot the data you obtain on a graph?
Cumulative time graph. This should result in a smooth curve
How can the displacement of the ball be determined from a vt graph?
The area under the graph
What equation can be used to determine the viscosity of the liquid?
(mg-4/3r^3gp)/6{pi}rv
How can the radius of a small ball be measured?
A screw gauge micrometer can be used to measure the diameter of the ball. Halve to give radius
