Answer:
45 N
Explanation:
The question can be solved by using Newton's second law:
F = ma
where
F is the net (unbalanced) force on the cyclist
m is the mass of the cyclist
a is his acceleration
In this problem:
m = 50 kg

Therefore, the unbalanced force is

The correct answer to the question is: Sound wave.
EXPLANATION:
Before going to answer this question, first we have to understand longitudinal wave.
A longitudinal wave is a mechanical wave in which the direction of propagation of wave is parallel to the direction of particle vibration.
This wave propagates through a medium in the form of compression and rarefaction.
Compression are the regions of high pressure zones where the particles of the medium are closely aggregated to each other.
Rarefaction is the region of low pressure where particles of the medium are not so close to each other as compared to compression.
The longitudinal wave can not propagate in space. It always needs a medium for it's propagation. The medium may be solid, liquid or gas .
For instance, sound wave is a longitudinal wave.
Hence, the correct answer of this question is sound wave which needs a medium for it's propagation.
Answer:
Explanation:
Given
Length of cable 
Diameter of cable 
time taken to return to original position 
time taken to cover distance L

velocity

(b)Relation between velocity of wave Tension is
mass per unit Length



where 



All of the forces listed are correct. There are 4 presently known forces.
Second question os B. the Lorentz force. It's given by
F=q(E+VxB) where q is the electric charge, E is the electric field, V is the particle's velocity vector, B is the magnetic flux density, and "x" represents the vector cross product.
The anwser would be A
hope this helped