In this experiment students use light gates to measure the distance and speed of a glider as it
slides down a sloping air track. Graphs of distance and speed versus time are drawn and students
discover the connections between the two - gradient and area.
Air track and large glider, 3 photogates, 2 electronic timers (IEC event timers are perfect),
Black/grey foam with dimensions 20 x 44 x 2 cm. The foam is slid into the groove in the glider
and acts as a flag to break the light beams in the gates
Top
2. Performance of a racing car
Students are given the performance curves of an imaginary racing car - a Pherary. The curves
show how its speed increases under acceleration, decreases under braking and how fast it can
go around corners of differing radius. They are given the lengths of the straights and the radii
of the corners of a circuit called Physics Park. The students then have to calculate how long it
will take the Pherary to do one lap of the track. Students can calculate distances by finding
areas under the graphs using the counting squares method. The equations of the acceleration and
braking curves are given. Students can calculate distances by using their graphic calculators to
determine the areas. Offer the students a chocolate bar for the first person who calculates the
lap time correct to the nearest tenth of a second. Solution is included.
No equipment needed, a graphics calculator is useful Top
3. Stopping Time and Distance
Students investigate the relationships between the time to stop, the distance to stop and the
speed of a car when a constant braking force is applied. The car is simulated with a cart that
has a mechanics/smart pulley attached. The braking is supplied by a constant up slope created
using a flexible plank with a stiffening board under the uphill section. Students set the
interface software to plot a speed versus time graph. From the graph and the listing of times
and distances logged, students determine the stopping time and distance and the initial speed
of the cart. They plot the graphs which show the relationships. Their findings are related to
road safety and they discover why cars travel a lot less distance when stopping if their speed
is a little less when the brakes are applied.
Cart, Mechanics/smart pulley, Interface, PC, flexible plank, Stiffening board, bricks/boxes
to support the board Top
4. Safe Driving Distance
In this exercise student analyse a line of moving cars. A child walks out onto the road.
The reaction time of the drivers and the stopping ability of the cars is used to plot the
positions of the cars each second as they come to a stop. Students discover how much distance
should be left between cars if they are all to stop safely in an emergency.
In this exercise the concept of acceleration is defined. Students analyse the increase in speed
of a car from rest to 28 m/s. Firstly when the car has constant acceleration, when it has
increasing acceleration and when it has decreasing acceleration. Zero to 28 m/s is chosen
because the numbers 0, 1, 3, 6, 10, 15, 21 and 28 come in very handy during the exercise!
Speed versus time graphs are plotted on the same axes. The gradients of the graphs are
related to the type of accelerations of the car. Acceleration versus time graphs are plotted
and the areas related to the change in speed of the car. The main aim of this exercise is to
show students the although you use speed to calulate acceleration, speed and acceleration are
two separate physical quantities.
In this experiment the equations of motion for an object with uniform acceleration are derived
and they are checked using the same apparatus as the Distance/time and Speed/time Graphs
experiment.
Air track and large glider, 3 photogates, 2 electronic timers (IEC event timers are perfect),
Black/grey foam with dimensions 20 x 44 x 2 cm. The foam is slid into the groove in the glider
and acts as a flag to break the light beams in the gates Top
7. Rolling Down a Slope
Students roll a cart down a slope. The cart has a mechanics/smart pulley attacked to it enabling
the PC to determine the acceleration of the cart. The relationship between acceleration and angle
of the slope is investigated. They discover that the sine of the angle is involved.
Stiff board about 150 cm long, cart, mechanics/smart pulley, interface, PC,
Protractor Top
