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Answer:
W= 4.4 J
Explanation
Elastic potential energy theory
If we have a spring of constant K to which a force F that produces a Δx deformation is applied, we apply Hooke's law:
F=K*x Formula (1): The force F applied to the spring is proportional to the deformation x of the spring.
As the force is variable to calculate the work we define an average force
Formula (2)
Ff: final force
Fi: initial force
The work done on the spring is :
W = Fa*Δx
Fa : average force
Δx : displacement
:Formula (3)
: final deformation
:initial deformation
Problem development
We calculate Ff and Fi , applying formula (1) :


We calculate average force applying formula (2):

We calculate the work done on the spring applying formula (3) : :
W= 11N*(0.7m-0.3m) = 11N*0.4m=4.4 N*m = 4.4 Joule = 4.4 J
Work done in stages
Work is the change of elastic potential energy (ΔEp)
W=ΔEp
ΔEp= Epf-Epi
Epf= final potential energy
Epi=initial potential energy




W=ΔEp= 5.39 J-0.99 J = 4.4J
:
Answer:
Magnification m is 2.5cm
Explanation:
This problem bothers on lenses
Given data
Object distance u= 4cm
Height of object v= 10 cm
The problem is quite straightforward seeing that object and image distances are given
We know that the magnification
m= size of image/size of object
m= v/u= 10/4 = 2. 5cm
What is a convex lens
A convex lens is a type of lens that has the centre thicker than the ends, the thickness at the centre makes the lens surface to curve outward. Convex lens causes close light rays of light to converge at a point after refraction.
Answer:
F=480.491 N
Explanation:
Given that
mass ,m = 22 kg
Angular speed ω = 40 rev/min

ω =4.18 rad/s
The radius r= 1.25 m
We know that centripetal force is given as
F=m ω² r
Now by putting the values in the above equation we get

F=480.491 N
Therefore the centripetal force on the child will be 480.491 N.