Hello!
I'm unfamiliar with the book you are reading,
However, based on textual evidence, I think your answer relies somewhere in answer choice A or D.
I hope this helps!
Answer:

Explanation:
Force on a current carrying rod due to magnetic field is given as

here we know that
current in the rod


now magnetic force is balanced by the weight of the rod
so we will have



Answer:
50 m/s
Explanation:
Angle = 60 degree
Horizontal component of velocity = 50 m/s
A projectile motion is the motion of an object in two dimensions under the influence of gravity.
In this case, the object has no acceleration along horizontal direction, it has acceleration in vertical direction which is equal to the acceleration due to gravity of earth.
When the projectile reaches at the maximum height it travels only along the horizontal and thus it has only horizontal velocity at that instant.
Thus, the velocity of teh projectile at maximum height is same as horizontal component of velocity that meas 50 m/s.
Answer:
1. bending of light in gravitational fields.
2. effect of gravitational redshift.
3. perihelion precission of mecury.
Explanation:
1 bending of light in gravitational fields, we can think of it like this:
by noting the change in position s of stars as they pass near the sun on the celetial sphere, so since the sun creates a gravitational field even the star thats not in our line of side(behind the sun) can be seen because its light is bent.
2. effects of gravitational redshift:
this says that if you are in the gravitational field, your clock moves slower when it is seen by a distant observer.
3. perihelion precission of mecury:
according to Newtonian physics a two body system consisting of a lone orbiting the spherical mass would trace out an ellipse with the center of mass of the system as the focus but mercury deviates from that precission. then according to Einstein, the change in orientation of the orbital ellipsewithin its orbital plane is the effect of gravitation being mediated by the curvature of space-time.