Answer:
Explanation:
Given
length of window 
time Frame for which rock can be seen is 
Suppose h is height above which rock is dropped
Time taken to cover 
so using equation of motion

where y=displacement
u=initial velocity
a=acceleration
t=time
time taken to travel h is

Subtract 1 and 2 we get


and from equation 
so 

and 
so 



substitute the value of
in equation 2


Answer:
static electricity and then lightning rod
The emerging velocity of the bullet is <u>71 m/s.</u>
The bullet of mass <em>m</em> moving with a velocity <em>u</em> has kinetic energy. When it pierces the block of wood, the block exerts a force of friction on the bullet. As the bullet passes through the block, work is done against the resistive forces exerted on the bullet by the block. This results in the reduction of the bullet's kinetic energy. The bullet has a speed <em>v</em> when it emerges from the block.
If the block exerts a resistive force <em>F</em> on the bullet and the thickness of the block is <em>x</em> then, the work done by the resistive force is given by,

This is equal to the change in the bullet's kinetic energy.

If the thickness of the block is reduced by one-half, the bullet emerges out with a velocity v<em>₁.</em>
Assuming the same resistive forces to act on the bullet,

Divide equation (2) by equation (1) and simplify for v<em>₁.</em>

Thus the speed of the bullet is 71 m/s
During upward projection the final velocity is zero, and the gravitational acceleration is -10 m/s² (against the gravity).
Therefore; using the equation;
S = 1/2gt² + ut
Where s is the height h, g is gravitational acceleration, and t is the time and u is the initial velocity u, is 16 ft/s.
Thus; h= 1/2(-10)t² + 16t
We get; h = -5t² + 16t
Therefore; the quadratic equation is 5t² - 16t + h =0
The magnitude of the charge on the balloon is 1.6 x 10⁻¹² C.
<h3>
What is the magnitude of the charge on the ball?</h3>
The magnitude of the charge on the ball is calculated by determining the total charge equivalent to the given number of electrons.
The charge of one electron = 1.6 x 10⁻¹⁹ Coulombs
Now, we are going to estimated the total charge of 1 x 10⁷ electrons.
1 electron = 1.6 x 10⁻¹⁹ C
1 x 10⁷ electrons = ?
= (1 x 10⁷ electrons x 1.6 x 10⁻¹⁹ C) / (1 electron)
= 1.6 x 10⁻¹² C
Thus, the total charge of 1 x 10⁷ electrons is obtained by multiplying the magnitude of charge of one electron to the entire given electrons.
Learn more about charge of electron here: brainly.com/question/9317875
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