Answer:

Explanation:
According to Coulomb's law, the magnitude of the electric force between two point charges is directly proportional to the product of the magnitude of both charges and inversely proportional to the square of the distance that separates them:

Here k is the Coulomb constant. In this case, we have
,
and
. Replacing the values:

The negative sign indicates that it is an attractive force. So, the magnitude of the electric force is:

Answer:

Explanation:
<u>Accelerated Motion
</u>
When a body changes its speed at a constant rate, i.e. same changes take same times, then it has a constant acceleration. The acceleration can be positive or negative. In the first case, the speed increases, and in the second time, the speed lowers until it eventually stops. The equation for the speed vf at any time t is given by

where a is the acceleration, and vo is the initial speed
.
The train has two different types of motion. It first starts from rest and has a constant acceleration of
for 182 seconds. Then it brakes with a constant acceleration of
until it comes to a stop. We need to find the total distance traveled.
The equation for the distance is

Our data is

Let's compute the first distance X1


Now, we find the speed at the end of the first period of time


That is the speed the train is at the moment it starts to brake. We need to compute the time needed to stop the train, that is, to make vf=0



Computing the second distance


The total distance is



Answer:
10500 J/kg/*C
Explanation:
Quantity of heat required=mass of substance x specific heat capacity x change in temperature
Quantity of heat required=0.25 x 4200 x [30-20]
Quantity of heat required=0.25 x 4200 x 10
Quantity of heat required=10500 J/kg/*C
An element would be the type of substance that only contains one kind of matter.