3.1 - techniques to investigate motion
to determine terminal velocity of a falling object, use light gates connected to a timer or data logger. time between 2 light beams being broken is recorded and used with distance between beams to calculate velocity.
this technique can be used to investigate conservation of momentum resulting from a collision using objects suspended on air track and strip of cardboard to interrupt light beam.
to determine g, electromagnet holds steel ball suspended a known distance above trapdoor. electromagnet deactivated and timed starts, stops when trapdoor hit.
another method: filming small metal ball falling against ruler, with known frames per second
3.2 - techniques to determine terminal velocity
fill a cylinder with a viscous liquid, hold a ball bearing over surface, release from rest and simultaneously start a timer and mark position of ball bearing within tube. When it reaches tv, distance travelled in each time interval will be the same so velocity can be determined.
To increase accuracy, set up a pulley system with ball bearing on one end and strip of tape passing through a ticker timer on the other end. Ticker timer produces 50 dots per second on tape, distance between dots and time used to determine tv.
3.2 - finding centre of mass
Freely suspend an object, centre of mass will rest vertically below its suspension point, suspend a plumb bob from a string directly in front of the object, draw a straight line along the string on the object. Suspend object from another point and repeat. Intersection of these points is centre of mass.
3.2 - finding density of an object
Measure mass using a balance
For a liquid, measure volume using a cylind e r
For a regular solid, measure volume using vernier callipers to find side lengths
For an irregular solid, use a eureka can
3.4 - techniques to investigate force-extension characteristics
This can be used to test materials such as springs, rubber bands, and polythene strips
Material is suspended using a clamp stand with a clamp and boss adjacent to a metre rule, attach a marker to the ruler to measure original length of material, attach standard masses to the bottom of the material, extension of spring for each mass is recorded
Reduce errors by reading values at eye level and using a set square to ensure ruler is straight
Calculate force constant by drawing a graph of force against extension and finding gradient
To reduce error only use straight line section of graph
3.4 - techniques and procedure to determine young modulus
Measure diameter of wire using micrometer, use several points and calculate an average to reduce error, calculate cross-sectional area, clamp wire at one end and place ruler with marker at end parallel to it. Apply different slotted masses to end and record mass and extension, calculate stress and strain and plot a graph, gradient gives young modulus
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