What is the main difference between mechanical and electromagnetic waves jiskha
1 answer:
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Answer:
(a) The parachutist spent 24.84 secs in air
(b) The height the fall begins is 472 m
Explanation:
Here is the complete question:
A parachutist bails out and freely falls 63 m. Then the parachute opens, and thereafter she decelerates at 1.5 m/s2. She reaches the ground with a speed of 3.3 m/s. (a) How long is the parachutist in the air (b) At what height does the fall begin?
Explanation:
From one of the equations of kinematics for free fall
Where H is the height
u is the initial velocity
t is the time
and g is the acceleration due to gravity (Take g = 9.8 m/s2)
Now, we can find the time spent before the parachute opens.
u = 0 m/s (we assume the parachutist starts from rest)
H = - 63 m
∴
This the time spent before the parachute opens
Also from one of the equations of kinematics for free fall
where v is the final velocity
We can determine the final velocity before the parachute opens and she starts to decelerate
∴
Now, we will calculate the time spent after the parachute opens
From one of the equation of kinematics for linear motion,
Here, the initial velocity will be the final velocity just before the parachute opens, that is
From the question,
We then get
(a) To determine how long the parachutist is in the air,
That is sum of the time used when falling freely and the time used after the parachute opens
= 3.59 secs + 21.25 secs
24.84 secs
Hence, the parachutist spent 24.84 secs in air
(b) To determine what height the fall begins
First, we will calculate the height from which the parachute opens
From one of the equation of kinematics for linear motion,
≅
Hence, the height the fall begins is 63m + 409m
= 472 m
Answer:
n=6.56×10¹⁵Hz
Explanation:
Given Data
Mass=9.1×10⁻³¹ kg
Radius distance=5.3×10⁻¹¹m
Electric Force=8.2×10⁻⁸N
To find
Revolutions per second
Solution
Let F be the force of attraction
let n be the number of revolutions per sec made by the electron around the nucleus then the centripetal force is given by
F=mω²r......................where ω=2π n
F=m4π²n²r...............eq(i)
as the values given where
Mass=9.1×10⁻³¹ kg
Radius distance=5.3×10⁻¹¹m
Electric Force=8.2×10⁻⁸N
we have to find n from eq(i)
n²=F/(m4π²r)