Answer:
Let No be initial no of atoms
N = N0 / 2 after 1 half-life
N = N0 / 4 after 2 half-lives
So after 2 half-lives 20 of the 80 atoms remain
Answer:
B
Explanation:
it's converts electrical energy to mechanical energy.
Efficiency is calculated through dividing the actual mechanical advantage by the hypothetical mechanical advantage:
- the actual mechanical advantage is 9J because that's how much work the light bulb doing
- the hypo. mechanical advantage is 100J. Ideally, in a perfect world, the light bulb can convert 100J input into 100J output, but do to resistance and other factors it is not possible.

change the decimal to a percentage:

the light bulb had 9% efficiency
Well formation of metallic bond depends on free electrons.smaal sized atoms hold their electrons more firmly as compared to large size atoms ,this z due to distance of outer shell electrons by nucleus..in this way no of free electrons affect strength of metallic bond..smaal sized atoms release less free electrons..
Answer:
F = 3.98 kN
Explanation:
GIVEN DATA:
sides of box = 17 cm
pressure = 1 atm = 101325 N/m2
T2 = 378K
T1 = 278 K
final pressure can be calculate by using below relation

we know that
force = pressure * area
therefore force is


F = 3.98 kN