Select all that apply.
no work is accomplished in which of the following situations?

a boy carried a 4.0-newton box 3.0 meters across the room at a constant velocity.
a boy pushes on a box weighing 4.0 newtons and it doesn't move.
a boy lifts a 4.0-newton box to a height of 1.0 meter.

a boy pushes on a box weighing 4.0 newtons and it doesn't move.

Explanation:

The definition of work is the following:

where

F is the force applied

d is the displacement

is the angle between the direction of the force and of the displacement

From the formula, we notice that if there is no displacement (d=0), then the work done is zero (W=0).

The choices given are:

a boy carried a 4.0-newton box 3.0 meters across the room at a constant velocity.  --> in this case, work is done (displacement is non-zero)

a boy pushes on a box weighing 4.0 newtons and it doesn't move.  --> in this case, NO work is done (because the displacement is zero)

a boy lifts a 4.0-newton box to a height of 1.0 meter. --> in this case, work is done (displacement is non-zero)

So, the correct choice is

a boy pushes on a box weighing 4.0 newtons and it doesn't move.

part 1: which substance has a higher solubility?

a

smallest amount left undissolved atall temps in table shown most has dissolved high sol'by

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =