Inside the torch, they usually use copper or brass to conduct electricity.
Kinetic energy because the ball is in motion or moving with energy behind it... kinda like when you shoot a gun, the bullet is fired out of the muzzle with kinetic energy ( Punch ) and the bullet goes through a wall or something. Sorry but my math skills aren't very good to give complex calculations but I would recommend that you maybe talk to some of the top ranking math guys on the website. Maybe they can give you better help...
Anyways, I hope I have been helpful to you.
N<span>o net external force acts on the system </span>
6. 0N. This questions requires understanding of how friction functions. Friction is a resistive force, meaning it opposes the direction of any applied or unbalanced forces. The box in the question experiences no horizontal force, so there is no resistive force in response to it, making it 0N.
7. This question tests your understanding of static friction. Static friction only applies when an applied or unbalanced force is applied to an object which does not move. The static friction always equals the magnitude of the applied or unbalanced force component parallel to the surface which the object rests on. The question states that the crate starts to move only when the applied force exceeds 313N, so we use this value to determine the force of static friction. The additional info in the question pertaining to when the crate is moving is irrelevant when determining static friction (only relevant if determining kinetic friction). Knowing this we solve for the weight of the crate:
F = mg
F = (45)(9.8)
F = 441N = Normal Force
The weight of the crate is also equal to the Normal Force since the object rests on a horizontal surface and the applied force is horizontal as well. In this question, since the object is not moving at 313N of applied force, the magnitude of static friction equals the applied force:
Ff = μs * Fn
(313) = μs (441)
0.71 (rounded) = μs
