Answer:
<em>mass</em>
<em></em>
Explanation:
Density is the measure of how much mass of a substance is squeezed into a given volume of that substance. <em>It is the mass per unit volume</em>, and substances with lesser density will float in materials with denser density. Buildings are generally more obviously denser that air, if not we'll see then float upwards into the atmosphere, but that is not the case. Different liquids too can separate and form layers on one another due to their differences in volume.
Radiation is the flow of energy by means of electromagnetic waves.
Answer:
The magnitude of force is 1.86 N and the direction of force is towards the other wire.
Explanation:
Given:
Current flowing through each power line, I = 130 A
Distance between the two power lines, d = 40 cm = 0.4 m
Length of power lines, L = 220 m
The force exerted by the power lines on each other is given by the relation:

Substitute the suitable values in the above equation.

F = 1.86 N
Since the direction of current flowing through the power lines are opposite to each other, so the force is attractive in nature. Hence, the direction of force experienced by the power lines on each other is towards the each other.

Explanation:
Natural length of a spring is
. The spring is streched by
. The resultant energy of the spring is
.
The potential energy of an ideal spring with spring constant
and elongation
is given by
.
So, in the current problem, the natural length of the spring is not required to find the spring constant
.

∴ The spring constant of the spring = 
You are running at constant velocity in the x direction, and based on the 2D definition of projectile motion, Vx=Vxo. In other words, your velocity in the x direction is equal to the starting velocity in the x direction. Let's say the total distance in the x direction that you run to catch your own ball is D (assuming you have actual values for Vx and D). You can then use the range equation, D= (2VoxVoy)/g, to find the initial y velocity, Voy. g is gravitational acceleration, -9.8m/s^2. Now you know how far to run (D), where you will catch the ball (xo+D), and the initial x and y velocities you should be throwing the ball at, but to find the initial velocity vector itself (x and y are only the components), you use the pythagorean theorem to solve for the hypotenuse. Because you know all three sides of the triangle, you can also solve for the angle you should throw the ball at, as that is simply arctan(y/x).