Acceleration can be defined as the change of speed in an instant of time, that is

Here,
Final velocity
Initial velocity
Change in time
From this expression we will calculate the requested values replacing the variables in each of the given terms
PART A) The values under this condition are:



Replacing,


PART B ) The values under this condition are:



Replacing,


Therefore the acceleration in the second time interval is
PART C) The values under this condition are:



Replacing,


<span>The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object. </span>
Answer:
The force between charges is
.
Explanation:
The Coulomb force
between the two charges
and
separated by distance
is given by the equation

where
is the coulombs constant, and has the value
.
Now in our case

and
,
therefore, the Coulomb force between the charges is


Answer:
W = 7000 J
Explanation:
To solve this problem we use that the speed of the bicycle is constant, therefore its acceleration is zero
F -fr = 0
F = fr
where F is the force applied by the child
Work is defined by
W = F. x
W = F x cos θ
in this case the child's force is parallel to the movement, therefore the angle is zero and cos 0 = 1
let's calculate
W = 35 200
W = 7000 J