Answer: C
X = Displacement of the spring
Hooke's law: It states that the applied force F is proportional to the displacement of spring .
F ∝ x
Where, x = displacement of spring in meters
F = force, measured in Newtons
In another words The force F is equal to the constant K times the disparagement.
F = k.x
Where k is constant and it depends on elastic material.
Spring has restorative force.
If the spring moves in opposite direction then,
F = - k.x
A negative sign indicates that the spring resists and force is to the left. The compression of the spring is greater than the restoring force.
Example: A mass 'm' stretches a spring at a displacement x.
Answer:
(a)

(b)
1120 N
Explanation:
Change in velocity,
is given by subtracting the initial velocity from the final velocity and expressed as 
Where v represent the velocity and subscripts f and i represent final and initial respectively. Since the ball finally comes to rest, its final velocity is zero. Substituting 0 for final velocity and the given figure of 8 m/s for initial velocity then the change in velocity is given by

To find
then we substitute 7 kg for m and -8 m/s for
therefore 
(b)
The impact force, F is given as the product of mass and acceleration. Here, acceleration is given by dividing the change in velocity by time ie

Substituting t with 0.05 s then 
Since F=ma then substituting m with 7 Kg we get that F=7*-160=-1120 N
Therefore, the impact force is equivalent to 1120 N
The first: alright, first: you draw the person in the elevator, then draw a red arrow, pointing downwards, beginning from his center of mass. This arrow is representing the gravitational force, Fg.
You can always calculate this right away, if you know his mass, by multiplying his weight in kg by the gravitational constant

let's do it for this case:

the unit of your fg will be in Newton [N]
so, first step solved, Fg is 637.65N
Fg is a field force by the way, and at the same time, the elevator is pushing up on him with 637.65N, so you draw another arrow pointing upwards, ending at the tip of the downwards arrow.
now let's calculate the force of the elevator

so you draw another arrow which is pointing downwards on him, because the elevator is accelating him upwards, making him heavier
the elevator force in this case is a contact force, because it only comes to existence while the two are touching, while Fg is the same everywhere
Answer:
1. telescope
2.

f- focal length
f- focal length r- the radius of curvature of the mirror

p-the distance of the object from the vertex of the mirror
l-the distance of the figure from the vertex of the mirror
Answer:
The resultant vector is 1 m/s
Explanation:
The resultant vector is 1 m/s west based on triangle law of vector addition, when two sides of a triangle is represented by two vectors, the resultant vector is the third side of the triangle.