Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole<span> reversal about every 200,000 to 300,000 years, although it has been more than twice that </span>long<span> since the last reversal.</span>
initial height of the Pole - vaulter = 4.2 m
now when he reached the top of the pad his height is 80 cm
so the total displacement of the person will be = 4.2 - 0.8 = 3.4 m
now we can use kinematics to find the speed just before he touch the pad




now when he compressed on pad the distance after which he will stop is 50 cm
so now again using kinematics we can say



so it is acceleration by -66.64 m/s^2
We know that frequency is an inverse value of time
this implies that time is the inverse value of frequency
.
Now since <em>f</em> is <em>40kHz</em><em>,</em><em> </em>we can calculate period or duration for that matter time.

Hope this helps.
r3t40
According to the Law of Conservation of Charge, the net
charge remains constant. If both things have different charges, upon contact,
they would share the charge equally. In this case, the total charge is -16μC.
The final charge for each ball would be -8 μC.
Answer:
Change in KE is 40 J
Explanation:
Recall that the impulse exerted on an object equal the change of momentum of the object (ΔP), which in time is defined as the product of the force exerted on it times the time the force was acting:
Change in momentum is: ΔP = F * Δt
In our case,
ΔP = 40 N * 1 sec = 40 N s
Since the object was initially at rest, its initial momentum was zero, and the final momentum should then be 40 N s.
So, the initial KE was 0, and the final (KEf) can be calculated using:
KEf = 1 /(2 m) Pf^2 = 1 / (40) 40^2 = 40 J
So, the change in kinetic energy is:
KEf - KEi = 40 J - 0 j = 40 J