Answer:
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
.
Answer:
harmful effects
1. that will cause air pollution
2. that will destroy our earth
Answer:

Explanation:
The acceleration of an object is given by Newton's second law:

where
F is the net force applied on the object
m is the mass of the object
For the book in the problem, we have:
is the mass
is the force applied
Substituting into the formula, we find the acceleration:

If I remember correctly, it is the 3rd answer choice.