Suppose that a block of mass 2 kg is pulled to the right with a force of 10 n, and the friction force on the block is directed to the left with a magnitude of 4 n. determine the acceleration of the block.

The block has an acceleration of

Explanation:

By means of Newton's second law it can be determine the acceleration of the block.

  (1)

Where represents the net force, m is the mass and a is the acceleration.

 (2)

The forces present in x are and (the friction force):

Notice that subtracts to since it is at the opposite direction.

The forces present in y balance each other:

Therefore:

 (3)

But and writing (3) in terms of a it is get:

So the block has an acceleration of .

the answer is b ) square root of 5

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 =