I need help with these questions : (see image )
Answer (b) and 19.
Note : these questions are under projectile.

The motion in which a body has constant horizontal component of velocity

but changing vertical component of velocity is called projectile motion. Every projectile body has PROJECTILE MOTION.

The Vertical Velocity will decrease during upward motion and increase during downward motion, by the factor,

Where,

Vf = final velocity

Vi = initial velocity  

Theta θ is the angle at which projectile is fired

g is acceleration due to gravity

t is time  

B) HORIZONTAL VELOCITY:

HORIZONTAL VELOCITY remains constant. According to Newton's 1st Law object in motion stays in motion until a force acts on it. There are no forces acting on a projectile in the horizontal direction (neglecting air resistance), therefore the velocity is constant.

Angle = θ(theta) = 30

Initial Velocity =

g = 10 m/s^2

Time taken to reach maximum height = T = ?

The time taken by the projectile to reach the maximum height is given by,

if you answer my question i will answer yours

3. dark matter

empty space could also be a simple vacuum