A constant velocity implies the two forces must be equal and opposite.
Friction acts horizontal to the ground, therefore we must find the force applied to the sled rope that acts horizontal to the ground.
Do this by resolving:
Force = 80cos53
The force opposing this is equal, and so also = 80cos53 = 48 N (2 sig. fig.)
The electrostatic force between two charges is given by Coulomb's law:

where
ke is the Coulomb's constant
q1 is the first charge
q2 is the second charge
r is the separation between the two charges
By substituting the data of the problem into the equation, we can find the magnitude of the force between the two charges:
The correct answer should be c.The kinetic energy of the water molecules decreases.
If the temperature drops that means that the molecules are coming together. If the temperature rises then it means that the molecules are spreading. If the kinetic energy falls down that means that they are slower which means that they are cooler.
Explanation:
Let
is the mass of proton. It is moving in a circular path perpendicular to a magnetic field of magnitude B.
The magnetic force is balanced by the centripetal force acting on the proton as :

r is the radius of path,

Time period is given by :


Frequency of proton is given by :

The wavelength of radiation is given by :


So, the wavelength of radiation produced by a proton is
. Hence, this is the required solution.
An LED is useful because when a current passes through it, it gives out light.