Answer:
1600 years half life
3200/1600 is 2 half lifes
first half life takes the sample to 1/2 it's original amount and the second takes it to 1/4 of it's original amount
so 1/4*7gm is 1.75gm
Explanation:
Answer:

Explanation:
As it is given that flow rate in the pipe is 20 cm^3/s
so we have

at the upper end the area is given as


Also at the other end


now the speed at two ends is given as




now by Bernoulli's theorem we have

now we have

Now we have

Answer:
Different surfaces have different impact force during collision which depends on the time it takes the person to come to rest after collision.
Explanation:
Given;
speed on concrete = 12 m/s (27 mi/h)
speed on soil = 15 m/s (34 mi/h)
speed on water = 34 m/s (76 mi/h)
The impact force on this person during collision is rate of change of momentum;

During collision, the force exerted on this person depends on how long the collision lasts; that is, how long it takes for this person to come to rest after collision with each of the surfaces.
The longer the time of collision, the smaller the force exerted by each.
It takes shorter time for the person to come to rest on concrete surface than on soil surface, also it takes shorter time for the person to come to rest on soil surface than on water surface.
As a result of the reason above, the force exerted on the person during collision by the concrete surface is greater than that of soil surface which is greater than that of water surface.
the answer is A it is so easy question
Answer:

Explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
a = Acceleration
m = Mass of bullet = 
r = Radius of barrel = 

Pressure is given by

The pressure of the expanding gas is 