Answer:
Work done, W = 19.6 J
Explanation:
It is given that,
Mass of the block, m = 5 kg
Speed of the block, v = 10 m/s
The coefficient of kinetic friction between the block and the rough section is 0.2
Distance covered by the block, d = 2 m
As the block passes through the rough part, some of the energy gets lost and this energy is equal to the work done by the kinetic energy.


W = 19.6 J
So, the change in the kinetic energy of the block as it passes through the rough section is 19.6 J. Hence, this is the required solution.
Answer:
Assuming that the length of the magnet is much smaller than the separation between it and the charge. As a result of magnetic interaction (i.e., ignore pure Coulomb forces) between the charge and the bar magnet, the magnet will not experience any torque at all - option A
Explanation:
Assuming that the length of the magnet is much smaller than the separation between it and the charge. As a result of magnetic interaction (i.e., ignore pure Coulomb forces) between the charge and the bar magnet, the magnet will not experience any torque at all; the reason being that: no magnetic field is being produced by a charge that is static. Only a moving charge can produce a magnetic effect. And the magnet can not have any torque due to its own magnetic lines of force.
Here in this question as we can see there is no air friction so we can use the principle of energy conservation


now here we know that



now plug in all values in above equation

divide whole equation by mass "m"



so height of the ball from ground will be 1.35 m
The answer would be 21.6 but rounded up it would be 22J.