Your solar transporter can’t drive as quickly with a heavy payload as
without one. The engine has to expend its force carrying the load.
Results
Your solar transporter can’t carry as big a payload up-
hill as it can on level ground. Since it is going uphill,
it not only has to move the weight in the driving direc-
tion, but also upward. So the slope has a considerable
influence on its maximum payload.
Experiment 24
>
You will need: light, solar transporter, large draw-
ing pad, blocks or small rocks as payload
Instructions
Now have your model drive down a slightly downhill
slope. Try changing the payload and see what hap-
pens.
Results
Going downhill, your solar transporter can carry an
even heavier payload than when it drives on level
ground.
Weight and Speed
In the next experiment, we will investigate the effect
that weight has on the vehicle’s speed. Speed is an
indication of how much time an object — a car, per-
son, or even a rolling ball — takes to cover a certain
distance. If you want to determine speed, you there-
fore have to know the precise values of two things:
the distance covered and the time. If, for example, a
car drives 50 kilometers per hour (km/h), that means
it drives a distance of 50 km in exactly one hour. If we
want to determine the precise speed of your solar car,
we will need a watch to measure time and a measur-
ing tape to measure distance.
Experiment 25
>
You will need: light, solar vehicle, a long mea-
suring tape, a stopwatch (you can also use a regular
watch if it has a second hand), paper and pen, a firm,
flat surface (for example, an asphalt sidewalk), bright
sunlight
Instructions
Mark off a distance of 1 m on the ground. Be sure that
the ground is flat and that your car won’t be driving
uphill or downhill. With a stopwatch, measure the
amount of time that your model takes to cover the
distance of 1 m when it isn’t carrying a payload. Note
down the number. Repeat the experiment with various
amounts of payload and compare the time values.
Results
The more payload you add to the cargo bed, the
slower your vehicle becomes. So there is a direct re-
lationship between weight and speed. You know this
relationship from your everyday life: You can walk a
lot faster when you aren’t carrying anything. The more
weight you carry, the less power is available to pro-
duce speed. It’s exactly the same with engines: their
power can either be applied to transporting a payload
or to driving fast.
The power of a vehicle’s engine is indicated in kilo-
watts (kw). Truck engines often produce as many kw
as the engine of a Formula One race car. Of course,
they are built quite differently. With trucks, the power
of the engine is used to transport as large a payload
as possible. With race cars, on the other hand, the
most important thing is to drive as fast as possible.
As a result, they can only carry a small payload.
With most of the cars you see on the street, the power
of the engine is geared in a variable way. This allows
them to carry a relatively large payload or climb a
steep hill in one gear, and drive very fast in another
gear.
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