A rock is dropped from a 200 m high cliff. How long does it take to fall (a) the first 100 m and (b) the last 50 m?
The basic equation you want is:
s=at22
Solving for t:
t=2sa−−−√
We’ll assume a=9.8 , so 2a−−√=14.9−−−√≈0.4518
So, for (a)s=100 , so t=0.4518100−−−√=4.518
The total time is 0.4518200−−−√≈6.389
The time to fall 150 m is 0.4518150−−−√≈5.533
So the time to fall the last 50 m is 6.389 - 5.533 = 0.856 seconds
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What could people do to DECREASE erosion of the Earth’s surface?
Well, People can plant crops or they can grow plants and if your looking at the options only B and C has that, but lets make sure. So A) "Cut down more trees" does not help DECREASE erosion, if you want to decrease erosion then you have to have roots to make earth's surface stay. A is eliminated, going to B, B says "Use more land to plant crops." that's better because crops have roots so it can keep the surface/land sucked in and will not get erode away. Anyways moving on to C, C "Allow natural vegetation to grow." that kinda helps decrease erosion; so imma keep that in mind, and finally D "Allow cattle to graze more often." does not help at all. So D and A is eliminated, So theres only C and B left, C will kinda help but B will help more; So it will leave us to the final answer which is....
Answer: B) Use more land to plant crops.
I hope this helps you and I hope you understand what i'm talking about...
From The Special, Idk, my name is weired I just picked this name. I wish I could change it.
Answer:


Explanation:
Given that
Q= 5 L/min
1 L = 10⁻³ m³/s
1 min = 60 s
Q=0.083 x 10⁻³ m³/s
d= 6 μm
v= 1 mm/s
So the discharge flow through one tube
q = A v


A=2.8 x 10⁻¹¹ m²
v= 1 x 10⁻³ m/s
q= 2.8 x 10⁻¹⁴ m³/s
Lets take total number of tube is n
Q= n q
n=Q/q


Surface area A
A= π d L


Solution:
f ( t )= 20 S ( t ) + 55/30 tS ( t )− 55/30 ( t − 30 ) S ( t − 30 )
• Taking the Laplace Transform:
F ( s ) = 20/s + 55/30 ( 1/s^2 ) – 55/30 ( 1/s^2) e^-30s = 20/s + 55/30 ( 1/s^2 ) ( 1 – e^-30s)
Answer:
Explanation:
b ) The problem is based on Doppler's effect of sound
f = f₀ x (V - v₀) /(
)
f is apparent frequency ,f₀ is real frequency , V is velocity of sound , v₀ is velocity of observer going away ,
is velocity of source going away
778 = 840 x (340 - 14)/ (340 +
)
340 +
= 341.18
= 1.18 m /s
it will go away from the observer or the cyclist.
speed of train = 1.18 m /s
a )
For a stationary observer v₀ = 0
f = f₀ x V /(
)
= 840 x 340 / (340 + 1.180)
= 837 Hz