As per given condition of point B we can see that height at point B is "h/2" from the ground
So we know that potential energy is given as
U = mgh
so here we have to put height h = h/2
so potential energy is U = mgh/2
now for kinetic energy we need to find the speed of it after falling the distance h/2
now by kinematics we will have

now for kinetic energy


now total energy will be given as

now for point C we can say that it is the point near to ground
So here height is ZERO
now potential energy will also be zero
U = 0
now for kinetic energy we need to find speed

now kinetic energy


now again we have total energy

Answer:
32.225 and angle is 48.7 degree.
Explanation:
u = 15, θ = 35 degree
v = 18, θ = 60
First represent the u and v in vector form.
u = 15 (Cos 35 i + Sin 35 j ) = 12.287 i + 8.6 j
v = 18 ( Cos 60 i + Sin 60 j ) = 9 i + 15.6 j
The sum of the two vectors is given by
u + v = 12.287 i + 8.6 j + 9 i + 15.6 j = 21.28 i + 24.2 j
Magnitude of u + v =
= 32.225
Let Ф be the angle
tan Ф = 24.2 / 21.28
Ф = 48.7 degree
Anyways the answer is x=2
speed=frequency*wavelength, so frequency=speed/wavelength. frequency=80*0.2
Frequency = 16 Hz