Aclassmate examines a substance that conducts electricity and is shiny but has no color. he says that is must be silver. what is his error?

He is making a conclusion from a single observation.

Silver isn’t the only metal that is shiny and has no colour.

For example, lithium, sodium, magnesium, and aluminium all have about the same colour as silver.

Not all materils that conduct electricity are silver.

Explanation:

The conductive materials are many and different. The best known are metals such as silver, gold, copper, aluminum.

But some aqueous solutions of salts are also conductive, even the human body is conductive.

As you can imagine, not all of these materials or solutions are silver or even shiny. So the mistake is in concluding that all conductive material must be silver and shiny, when that is not always the case.

it's c (engineer's do their work with mechanical stuff not on any living being)

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied