Which of the following is true A. If the sum of the external forces on an object is zero, then the object must be in equilibrium. B. If the sum of the external torques on an object is zero, then the sum of the external forces on it must also be zero. C. If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero. D. If an object remains at rest, then the sum of both the external torques and the external forces on the object must be zero. E. If the sum of both the external torques and the external forces on an object is zero, then the object must be at rest.

A. If the sum of the external forces on an object is zero, then the object must be in equilibrium

Explanation:

Equilibrium, in physics, the condition of a system when neither its state of motion nor its internal energy state tends to change with time.

For a single particle, equilibrium arises if the vector sum of all forces acting upon the particle is zero.

the object is at equilibrium, then the net force acting upon the object should be 0 Newton. Thus, if all the forces are added together as vectors, then the resultant force (the vector sum) should be 0 Newton.

There are three types of equilibrium: stable, unstable, and neutral

answer: the correct answer id option(d).

explanation:

snell's law refraction:

the angle of refraction =

the angle of incidence =

refractive index of air = = 1

refractive index of glycerol = 1.47

from the given options, the most closest answer to 63.72° is 65° of option (d).