Answer:
30 cm
Explanation:
To solve this problem, we use the lens equation:

where
f is the focal length of the lens
p is the distance of the object from the lens
q is the distance of the image from the lens
In this problem, we know that
q = -30 cm is the distance of the image from the lens; it is negative because the image is formed in front of the lens, so it is a virtual image
We also know that the size of the image is twice that of the object, so the magnification is 2:

where M is the magnification of the lens. Solving this equation for p,

So, the distance of the object from the lens is 15 cm.
Now we can finally solve the lens equation to find f, the focal length:

Answer:False
Explanation:
the intensity of the sound wave decreases with increasing distance from the source.
Answer:
The small pebble
Explanation:
Since the potential energy, P.E lost equals kinetic energy, K.E gained,
P.E = K.E
P.E = mgh = K.E
So, K.E = mgh where g = acceleration due to gravity and h = height of drop
Since h and g are constant
K.E ∝ m
So, the kinetic energy of the object is directly proportional to its mass. Thus, the object with the smaller mass has the lesser kinetic energy.
Since the object with the smaller mass is the small pebble, so the small pebble would have less kinetic energy as it crashes on the road at the bottom of the mountain.
Answer:
Increasing its surface area
Explanation:
In Science, increasing the surface area of a gas increases its collision rate and is one evolutionary strategy that has maximized gas diffusion by catalysing the rate of gaseous reaction.
Answer:
A
Explanation:
A disadvantage is that sexual reproduction takes longer than asexual reproduction. A mate must be found, the egg must be fertilised by sperm, and then the offspring develop. ... This means that some individuals would survive and be able to reproduce and generate more offspring.