Internal energy of the system changes by ΔE = 178 J.
Heat given to the system = Q = +658 J.
According to the first law of thermodynamics,
ΔE = Q + W
178 = 658 + W
∴ W = 178-658 = -480 J
Minus sign indicates that work is done by the system.
Via half-life equation we have:

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes. By plugging those values in we get:

There is 6.25 grams left of Ra-229 after 12 minutes.
Answer:
F = 326.7 N
Explanation:
given data
mass m = 200 kg
distance d = 2 m
length L = 12 m
solution
we know force exerted by the weight of the rock that is
W = m × g ..............1
W = 200 × 9.8
W = 1960 N
and
equilibrium the sum of the moment about that is
∑Mf = F(cos∅) L - W (cos∅) d = 0
here ∅ is very small so cos∅ L = L and cos∅ d = D
so F × L - W × d = 0 .................2
put here value
F × 12 - 1960 × 2 = 0
solve it we get
F = 326.7 N
Answer:
<u>Option-(A): </u>A new moon is quite near the Sun in the sky.
Explanation:
- While the position of the new moon inside our sky has such an orientation that we are not able to see or observe the actual position and shape of the new moon.
- As the path or revolution is much more elliptical then we can imagine, for the moon there are certain position of motion inside the celestial space that for some times it looks for different then the other and such position generates the concept of a new moon.