Closed system. If the system is not closed, matter or energy can escape from the system. an example of this is if you react magnesium and hydrochloric acid in a open system. The H₂ gas is going to escape making it look like some of the mass disappeared . in that same reaction some in an open system will also loose heat to the surrounding which will make it look like less heat was produced.
Answer:
Work done, W = 100 J
Explanation:
We have, Billy the friendly Robot uses 50 N of force to lift a box 2 meters in the air.
It is required to find the work done by Billy.
Work done by an object is given in terms of force and displacement. The formula used to find the work done is given by :

So, the work performed by Billy is 100 J.
Is this supposed to be a question?????
B. is ur answer I bieleve
Answer:
The false statement is :
- Pyrite is an ore of gold and is used in jewelry making.
- Cobalt is not used in medicine.
Explanation:
Pyrite is an ore of iron sulfide found on the Earth and in coal, limestone and in many deposits of metallic ores. Due to its luster and pale yellowish color it appears as gold due to which it is also termed as Fool's gold.
It is used in firearms , in production of sulfur dioxide gas, etc.
Cobalt is used as medicine to treat cancer patient. Co-60 is used in treatment of cancer in which gamma rays produced by Co-60 are used to kill tumor cells in a cancer patient.
Where as talc is used in industries like : paper making, food, paints, plastics etc. Quartz is primary material used to prepare glass and cobalt is used as