Why do adults make bigger splashes when they jump into swimming pools than small children?
1 answer:
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(a) No, because the mechanical energy is not conserved
Explanation:
The work-energy theorem states that the work done by the engine on the airplane is equal to the gain in kinetic energy of the plane:
(1)
However, this theorem is only valid if there are no non-conservative forces acting on the plane. However, in this case there is air resistance acting on the plane: this means that the work-energy theorem is no longer valid, because the mechanical energy is not conserved.
Therefore, eq. (1) can be rewritten as
which means that the work done by the engine (W) is used partially to increase the kinetic energy of the airplane () and part is lost because of the air resistance (
).
(b) 77.8 m/s
First of all, we need to calculate the net force acting on the plane, which is equal to the difference between the thrust force and the air resistance:
Now we can calculate the acceleration of the plane, by using Newton's second law:
where m is the mass of the plane.
Finally, we can calculate the final speed of the plane by using the equation:
where
is the final velocity
is the initial velocity
is the acceleration
is the distance travelled
Solving for v, we find
Answer:
Part a)
Part b)
Part c)
Part d)
Explanation:
Part a)
While bucket is falling downwards we have force equation of the bucket given as
for uniform cylinder we will have
so we have
now we have
now we have
Part b)
speed of the bucket can be found using kinematics
so we have
Part c)
now in order to find the time of fall we can use another equation
Part d)
as we know that cylinder is at rest and not moving downwards
so here we can use force balance