Which of these statements about machines is false?
a. Machines decrease the amount of work needed to do a job
b. Machines decrease the force needed to get the work done,
c. Machines increase the distance moved in doing the work
d. Because of friction, the work input is more than the output

a. Machines decrease the amount of work needed to do a job

Explanation:

Machine is a mechanical device which reduce our efforts and makes the work simpler

So We know that the machine is a device which always reduce the work required

so here correct answer will be

a. Machines decrease the amount of work needed to do a job

i don't know, you need to give me some answers.

explanation:

answer: the rock sample is a sedimentary rock.

explanation:

it is given that:

mass of rock sample, m = 2.7 g

volume of rock sample,

so, density of rock sample will be

since, the density of rock sample is . hence, the rock sample is a sedimentary rock, whose densities varies between .