Identify the variables in the investigation: An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different size nails were used. The number of paper clips the electromagnet could pick up was measured.

Independent: sizes of nails

Dependent: number of paper clips

Controlled: Battery, wire and type of nails

Explanation:

An independent variable is a variable which when changes does not the effect the results of the experiment. It does not depends upon the dependent variable.

A dependent variable is defined as a variable which is affected when the independent variable is changed by the researcher or the experimenter. It depends greatly upon the independent variable.

While a controlled variable is that variable whose value is not changed in an experiment. It contains all the constants.

In the context,

the independent variable are : sizes of nails

the dependent variables are : number of paper clips

the Controlled variables are: Battery, wire and type of nails

what is the general relationship between a galaxy's distance from earth and its speed?

the answer is:

the farther away a galaxy is from us, the faster it is moving away from us.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.