Answer:
a) -4 N
b) +4 N
Explanation:
Draw a free body diagram for each block.
For the large block, there are 2 forces: 12 N pushing to the right, and F pushing to the left.
For the small block, there is 1 force, F pushing to the right.
There are also weight and normal forces in the vertical direction, but we can ignore those.
Sum of forces on the large block in the x direction:
∑F = ma
12 − F = 4a
Sum of forces on the small block in the x direction:
∑F = ma
F = 2a
2F = 4a
Substitute:
12 − F = 2F
12 = 3F
F = 4
The small block pushes on the large block 4 N to the left (-4 N).
The large block pushes on the small block 4 N to the right (+4 N).
Answer:
Option B

Explanation:
Given information
Radius of container, r=12cm=12/100=0.12m
Angular velocity= 2 rev/s, converted to rad/s we multiply by 2π
Angular velocity, 
We know that speed, 
Centripetal acceleration,
and substituting
we obtain that

Substituting \omega for 12.56637061 and r for 0.12

Rounded off, 
Answer:
The speed of this light and wavelength in a liquid are
and 442 nm.
Explanation:
Given that,
Wavelength = 650 nm
Index refraction = 1.47
(a). We need to calculate the speed
Using formula of speed

Where, n = refraction index
c = speed of light in vacuum
v = speed of light in medium
Put the value into the formula



(b). We need to calculate the wavelength
Using formula of wavelength


Where,
= wavelength in vacuum
= wavelength in medium
Put the value into the formula


Hence, The speed of this light and wavelength in a liquid are
and 442 nm.
Answer:
Explanation:
Average acceleration
is the variation of velocity
over a specified period of time
:
Where:
being
the initial velocity and
the final velocity (according to the information given from the described graph)

Then:
Answer: When a pathogen enters their colony, ants change their behavior to avoid the outbreak of disease. In this way, they protect the queen, brood and young workers from becoming ill. These results, from a study carried out in collaboration between the groups of Sylvia Cremer at the Institute of Science and Technology Austria (IST Austria) and of Laurent Keller at the University of Lausanne, are published today in the journal Science.
Explanation: search for it.