Answer:
After 80 years there will be 3 g of element X remaining
Explanation:
Given;
the half life of element X = 20 year
initial mass of element X = 48 g
a) How much is there after 80 years
0 year --------------------------> 48 g
20 years -----------------------> (48g / 2) = 24 g
40 years ------------------------> 12 g
60 years ------------------------> 6 g
80 years --------------------------> 3 g
Therefore, after 80 years there will be 3 g of element X remaining.
On a part-time job, you are asked to bring a cylindrical iron rod of density 7800 kg/m3 , length 92.8 cm and diameter 2.05 cm from a storage room to a machinist, the weight of rod w is 23.41 N .
<h3>How is the weight calculated?</h3>
Given ,
density (d) = 7800 kg/m³
D = 2.05 cm = 0.0205 m
r = D/2 = 0.0205 / 2 =0.01025 m
h = 92.8 cm = 0.928 m
The weight is calculated by ,
W = m × g
But, to find mass (m)
m = d × V
The volume of the rod, because is cylindrical, is,
V = π × r² × h
∴ V = 3.14 × (0.01025)² × 0.928
∴ V = 3.14 × 1.051 × 10⁻⁴ × 0.928
∴ V = 3.0625 × 10⁻⁴
Now to calculate mass,
m = d × V
∴ m = 7800 × 3.0625 × 10⁻⁴
∴ m = 2.3887 Kg
Now, for calculating weight
W = m × g
∴ W = 2.3887 × 9.8
∴ W = 23.41 N
∴ The weight of the rod W assuming the free-fall acceleration is 23.41 N .
<h3>What is weight?</h3>
- The weight of an object is the force exerted on it by gravity.
- It is define weight as a vector quantity, the force of gravity acting on an object.
- Some define weight as a scalar quantity that is the magnitude of gravity.
Can learn more about weight calculation from brainly.com/question/15685221
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Answer:
E=h.f
=5.2×1014×6.63×10^-34
E=3.496×10^-30 J
Then the coin will float on the surface of the liquid in the eishimg well.
