Answer:
It takes 28 days.
Explanation:
Hi there!
The half-life is the time at which the concentration of a substance is halved. For radon, it is 4 days. Then, after 4 days, the amount of radon present in the source will be 1/2 of its original concentration. After another 4 days, the concentration of radon will be half of the half of its original concentration, that is, 1/4 of the amount of radon originally present.
After another 4 days, the concentration will be halved again (1/4 /2 = 1/8) and after another 4 days, it will be halved again (1/8 / 2 = 1/16) and so on.
Then, after n half-lives, the concentration of radon will be reduced by a factor of 1/2ⁿ.
Then, to know how many half-lives it takes for the concentration of radon to be reduced to 1/128 of its original level, let´s solve this equation for n:
1/2ⁿ = 1/128
2ⁿ = 128
log 2ⁿ = log 128
n log 2 = log 128
n = log 128 / log 2
n = 7
After 7 half-lives, the concentration of radon will be reduced by 1/128. Since a half-life is 4 days, 7 half-lives will be (7 · 4) 28 days.
Answer:
D) 3.0
Explanation:
As we know that
So,
Now
T = True weight of object
= mg
= 245 N
W = apparent weight = 200 N
= density of object
Now we use the formula
buoyancy force = True weight - W
600 V (9.8) = 45
V = 0.007653
m = 25 kg
And as we know that
= 3266.7
Now
specific gravity is
= 3.2
Hence, the correct option is d.
It is in the noble gas group which has a full valence electron shell found in group 18
Answer:
(a) -1.18 m/s
(b) 0.84 m/s
Explanation:
(a)
The total linear momentum before the lumberjack begins to move is zero because all parts of the system are at res
From the law of conservation of momentum
m1v1+m2v2=0 hence m1v1=-m2v2 where m1 is mass of lumberjack, v1 is velocity of lumberjeck, m2 is mass of floating log, v2 is velocity of the floating log.
Substituting M1 for 103 Kg, V1 for 2.93 m/s, M2 for 255 Kg into the above equation we obtain
103Kg*2.93 m/s=-255Kg*V2
V2=-(103 kg*2.93 m/s)/255=-1.183490196 m/s
Hence V2=-1.18 m/s
(b)
For the second log
V(M1+M2)=m1v1 where V is the common velocity
V(103 Kg+255 Kg)=103 Kg*2.93 m/s
V=(103 Kg*2.93 m/s)/(103 Kg+255 Kg)=0.842988827 m/s
V=0.84 m/s
Answer:
-2.25
Real and inverted image
Explanation:
u = Object distance = 16 cm
v = Image distance = 36 cm
f = Focal length
Lens Equation
Focal length of the lens is 11.07 cm. Positive value indicates the lens is a convex lens
Magnification
Since magnification is negative the image inverted