Magnetism is <span>a physical phenomenon produced by the motion of electric charge, resulting in attractive and repulsive forces between objects.</span>

Explanation:
The acceleration due to gravity g is defined as

and solving for R, we find that

We need the mass M of the planet first and we can do that by noting that the centripetal acceleration
experienced by the satellite is equal to the gravitational force
or

The orbital velocity <em>v</em> is the velocity of the satellite around the planet defined as

where <em>r</em><em> </em>is the radius of the satellite's orbit in meters and <em>T</em> is the period or the time it takes for the satellite to circle the planet in seconds. We can then rewrite Eqn(2) as

Solving for <em>M</em>, we get

Putting this expression back into Eqn(1), we get




Answer:
W = 735.75[J]
Explanation:
Work is defined as the product of force by distance. Therefore we can use the following equation.

where:
W = work [J] (units of Joules)
F = force [N] (units of Newtons)
d = distance = 3 [m]
But first, we must determine the force that is equal to the product of mass by gravity (weight of the body).
![F=m*g\\F=25*9.81\\F=245.25[N]](https://tex.z-dn.net/?f=F%3Dm%2Ag%5C%5CF%3D25%2A9.81%5C%5CF%3D245.25%5BN%5D)
![W=F*d\\W=245.25*3\\W=735.75[J]](https://tex.z-dn.net/?f=W%3DF%2Ad%5C%5CW%3D245.25%2A3%5C%5CW%3D735.75%5BJ%5D)
Answer:
(a)The work done by the man is -15.03J.
(b)The force exerted on the object is 127.4N.
Explanation:
Mass of the object pulled by the man is -13kg
Object is lifted 11.8 cm vertical with his teeth it means (displacement = +11.8cm = +0.118m)
Acceleration due to gravity is 
(a) <u>Calculating the work done</u>:
Work done = mgh
Where "m" is mass of an object, "g" is acceleration due to gravity and "h" is the displacement.


The work done by the man is -15.03J.
(b) <u>Calculating the force</u>:
Probably the man and the object are close to the exterior of the earth. If the rigidity required to maintained the object of consistent velocity interior the gravitational field of the earth is 
Thus the weight of the object is balanced by the force of the man's teeth on the object. That is
F = mg

F = 127.4N
The force exerted on the object is 127.4N.