Answer:
The acceleration required by the rocket in order to have a zero speed on touchdown is 19.96m/s²
The rocket's motion for analysis sake is divided into two phases.
Phase 1: the free fall motion of the rocket from the height 2.59*102m to a height 86.9m
Phase 2: the motion of the rocket due to the acceleration of the rocket also from the height 86.9m to the point of touchdown y = 0m.
Explanation:
The initial velocity of the rocket is 0m/s when it started falling from rest under free fall. g = 9.8m/s² t1 is the time taken for phase 1 and t2 is the time taken for phase2.
The final velocity under free fall becomes the initial velocity for the accelerated motion of the rocket in phase 2 and the final velocity or speed in phase 2 is equal to zero.
The detailed step by step solution to the problems can be found in the attachment below.
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Answer:

Explanation:
We are given that
Potential ,V=25 kV=
Distance,r =1 cm=
1 m=100 cm
Mass of electron, m=
Charge, q=
We have to find the final velocity of the electron.
Speed of electron,
Using the formula

v=
Hence, the final velocity of the electron=
Answer:
The net force exerted by these two charges on a third charge is 
Explanation:
Given that,
Third charge 
Distance
Suppose The magnitude of the force F between two particles with charges Q and Q' separated by a distance d. Consider two point charges located on the x axis one charge, q₁ = -12.5 nC , is located at x₁ = -1.650 m, the second charge, q₂ = 31.5 nC , is at the origin.
We need to calculate the total force will be the vector sum of two forces
Using Coulomb's law,

Put the value into the formula


We need to calculate the force will be to the negative charge with opposite charges
Using Coulomb's law,

Put the value into the formula


The force also will be to the negative side, charges with same charge sign
We need to calculate the net force exerted by these two charges on a third charge
Using formula of net force




Negative sign shows the negative direction.
Hence, The net force exerted by these two charges on a third charge is 
The air inside the pipes of a wind instrument vibrates. ... The result is longitudinal standing waves in the air column inside the pipe. The ends, whether open or closed, create nodes or antinodes in these standing waves.