Mechanics | Relativity Answers

A particle is projected with a sped of 25 m/s at 30° above the horizontal. Find the time taken to reach the highest point of the trajectory.
Find the magnitude and direction of the velocity after 2s.

What is Newton`s First Law of Motion?

a ball is kicked with 16 m/s horizontal velocity and 12 m/s vertical velocity. at what velocity it will hit the ground? how much time it will be in air??

a man throws a stone to hit a box located 75 m from him.the initial point and the box are in same plane.the initial velocity of the stone is 35 m/s.what is the angle of throwing the stone to hit the box?at exact midpoint of the throwing point and the box,a buckle of tree is at a height of 3.5 m from the throwing point.will the stone go up of the buckle or down of the buckle?

A Rod of mass M and length L stands vertically on a smooth horizontal surface. A particle of mass m travelling at speed u strikes the top of the rod and comes to rest. The angular velocity of the rod after the impact is

A particle is projected from ground at an angle θ with horizontal with speed u. The ratio of radius of curvature of its trajectory at point of projection to radius of curvature at maximum height is?
Options are
A)1/sin^2θ cosθ B)cos^2θ
C)1/sin^3θ D)1/cos^3θ

A rock is thrown at a window that is located 18m above the ground. The rock is thrown at an angle 40 degrees above the horizontal. The rock is thrown from a height of 2.00m above the ground with a speed of 30m/s and experiences no appreciable air resistance. If the rock strikes the window on its upward trajectory, from what horizontal distance from the window was it released???

At the instant the traffic light turns green, an automobile starts with a constant acceleration of 2.2m/s2
At the same instant a truck travelling with a constant speed of 95m/s overtakes and passes the automobile. How far beyond the same point will the automobile overtake the truck? How fast will the car be travelling at that instance?

If a ball is thrown vertically upward from the roof of 58.8 m , when will it fall on the earth??
the solution is like this
let the upper direction is positive
then we can write

-h=ut-1/2gt^2 and t=6s .

my question is why h =10 is used here. i have thrown the ball from 58.8m upward. then it should have a height to the up and when it will fall downward then after crossing the roof it should have a height of 58.8m. so why in these case that upper height is not used .

my same question is also for projectile thrown from a height. there, also the upper height is not counted why?? why only the given height is used to solve the problems.

does newton's third law is applicable for inelastic substance? how and why?