The final speed of an airplane is v = 92.95 m/s
The rate of change of position of an object in any direction is known as speed i.e. in other word, Speed is measured as the ratio of distance to the time in which the distance was covered.
Solution-
Here given,
Acceleration a= 10.8 m/s2 .
Displacement (s)= 400m
Then to find final speed of airplane v=?
Therefore from equation of motion can be written as,
v²=u²+ 2as
where, u is initial speed, v is final speed ,a is acceleration and s is displacement of the airplane. Therefore by putting the value of a & s in above equation and (u =0) i.e. the initial speed of airplane is zero.
v²= 2×10.8 m/s²×400m
v²=8640m/s
v=92.95m/s
hence the final speed of airplane v =92.95m/s
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g Generally the accepted value of acceleration due to gravity is 9.801 
as per the question the acceleration due to gravity is found to be 9.42
in an experiment performed.
the difference between the ideal and observed value is 0.381.
hence the error is -
=3.88735 percent
the error is not so high,so it can be accepted.
now we have to know why this occurs-the equation of time period of the simple pendulum is give as-![T=2\pi\sqrt[2]{l/g}](https://tex.z-dn.net/?f=T%3D2%5Cpi%5Csqrt%5B2%5D%7Bl%2Fg%7D)

As the experiment is done under air resistance,so it will affect to the time period.hence the time period will be more which in turn decreases the value of g.
if this experiment is done in a environment of zero air resistance,we will get the value of g which must be approximately equal to 9.801 
One situation in which force is created is when an object is moving and a force is created to stop that movement. Second situation is when an object is moving circularly and a force is created to move it towards the middle of the circle. The third situation is when a force is created that goes in the same direction as an object that is in movement.
An object's momentum is the product of its mass and its velocity:
p = mv
p is its momentum, m is its mass, and v is its velocity.
Given values:
p = -80kg×m/s
m = 8kg
Plug in these values and solve for v:
-80 = 8v
v = -10m/s
Choice D
A steel piano wire, of length 1.150 m and mass of 4.80 g is stretched under a tension of 580.0 N.the speed of transverse waves on the wire would be 372.77 m/s
<h3>What is a sound wave?</h3>
It is a particular variety of mechanical waves made up of the disruption brought on by the movements of the energy. In an elastic medium like the air, a sound wave travels through compression and rarefaction.
For calculating the wave velocity of the sound waves generated from the piano can be calculated by the formula
V= √F/μ
where v is the wave velocity of the wave travel on the string
F is the tension in the string of piano
μ is the mass per unit length of the string
As given in question a steel piano wire, of length 1.150 m and mass of 4.80 g is stretched under a tension of 580.0 N.
The μ is the mass per unit length of the string would be
μ = 4.80/(1.150×1000)
μ = 0.0041739 kg/m
By substituting the respective values of the tension on the string and the density(mass per unit length) in the above formula of the wave velocity
V= √F/μ
V=√(580/0.0041739)
V = 372.77 m/s
Thus, the speed of transverse waves on the wire comes out to be 372.77 m/s
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