Question 4: Scientists and engineers often plan investigations to see how changing one variable affects the outcome. A variable is any trait, condition or feature of something being tested. Imagine a team is testing the speed of a toy car. In trial 1, they test the car and measure how long it takes it to travel 2 meters. In trial 2, they want to investigate how changing a variable affects the car's speed. Which of the following plans is BEST for trial 2?

A variable, as its name implies, is something that can change, ideally, as the scientists and engineers want to.

Particularly we care for the independent variables, which are the ones we can control and affect the dependent variables, which are the outcomes we study.

For a quick example, think of an experiment where you heat something on an oven. The temperature of the oven can be set by the scientist, so the temperature is an independent variable because they can control it.

Now let's see the given experiment.

The team is testing the speed of the toy car.

remember that:

distance/time = speed.

We know that in the first trial, they test how long takes the car to travel 2 meters.

Now, what we can change for the second trial, knowing that the speed is the output that we are studying?

The answer is trivial, the only thing we can change in the given setup is the distance that the car travels, so in the next trial we should change the variable "distance travelled by the car" and see if it affects the output "speed of the car".

If you want to learn more about variables, you can read:

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.