The radius of the sphere is r=5.15 cm=0.0515 m, and its surface is given by
So the total charge on the surface of the sphere is, using the charge density
:
The electrostatic force between the sphere and the point charge is:
where
ke is the Coulomb's constant
Q is the charge on the sphere
is the point charge
r is their separation
Re-arranging the equation, we can find the separation between the sphere and the point charge:
When a magnet is moved into a coil of wire, changing the magnetic field and magnetic flux through the coil, a voltage will be generated in the coil according to Faraday's Law.
Answer: a) 8.2 * 10^-8 N or 82 nN and b) is repulsive
Explanation: To solve this problem we have to use the Coulomb force for two point charged, it is given by:
Replacing the dat we obtain F=82 nN.
The force is repulsive because the points charged have the same sign.
Answer:
Under assumption that all food energy that needs the horse is transformed into work, then the horse needs approximately 3 megajoules of food energy to work for 1 hour.
Explanation:
Since horse is working steadily, the power experimented by the horse (
), measured in watts, is at constant rate. Then, the work needed by the horse (
), measured in joules, is equal to that power multiplied by time (
), measured in seconds. That is:
(1)
If we know that 
and 
, then the work needed for the horse is:
Under assumption that all food energy that needs the horse is transformed into work, then the horse needs approximately 3 megajoules of food energy to work for 1 hour.
So the initial velocity is 15 m/s, the final velocity is 0 since it's at a complete stop and time is 10 seconds. Therefore:
Therefore, the acceleration is -1.5 m/s^2. The reason it's negative is due to the fact that the vector is going against it's original movement since it's decelerating.
