Answer:
Option d is correct.
Explanation:
We know , resistance of a body is directly proportional to its length and inversely proportional to its area.
( Here, 
is constant dependent on object material )
Writing 
also :
( since they are of same material therefore, is same.)
Now , if 
.
Then 
Therefore, option d. is correct.
Hence, this is the required solution.
Answer: 2.82m/s
Explanation:
Wave speed(v) is the product of the frequency (f) of a wave and its wavelength (¶)
V = f¶
Since wavelength is the distance between two successive crests or trough, the wavelength given is 1.40m i.e ¶ = 1.40m
If the total crest is 25, this means that 25 oscillations occurs in 12.4s.
Since the number of oscillation made in one second is the frequency, frequency = 25/12.4 = 2.01cycle/seconds
Speed of the wave v = 2.01×1.4
V =
Wave speed is 2.82m/s
Answer:
548800J
Explanation:
Given parameters:
Mass of roller coaster = 800kg
Height of hill = 70m
Unknown:
Change in potential energy = ?
Solution:
The change in potential energy is the difference between the potential energy at the bottom and at the top.
Potential energy at the bottom is 0J
So;
Change in potential energy = mgh - 0
m is the mass, g is the acceleration, h is the height
Change in potential energy = 800 x 9.8 x 70 = 548800J
A). If the half-life is 40 days, then 5 half-lives = (5 x 40) days.
b). If 5 half-lives have passed, then the radioactive portion of
the sample has been cut in half five times.
The amount that remains is (1/2)⁵ of the original amount.
That's (the original amount) x (1/2 · 1/2 · 1/2 · 1/2 · 1/2)
or
(the original amount) / 2⁵
or
(the original amount) / 32 .
