T = half life period of decay for atoms of element A = 20,000 years
N₀ = initial number of atoms of element A = 10,000 atoms
N = final number of atoms after time "t" = 2500 atoms
t = time of decay = ?
λ = decay constant = ?
decay constant is given as
λ = 0.693/T
λ = 0.693/20,000
λ = 0.00003465 years⁻¹
atoms after decay for time "t" is given as
N = N₀
inserting the values
2500 = (10000)
t = 40,000 years
so correct choice is
B) 40,000 years
Answer:
72 km/h
Explanation:
Speed of car = 20m/s
So, here to find the speed in km/h we will change the metre to km and seconds to hours .
=>
= 72 km/hr
to change into km divide by 1000
(1 m = 1/1000km)
and,
to change into hours divide by 60*60= 3600
help kiya kya?
The key to solve this problem is the conservation of momentum. The momentum of an object is defined as the product between the mass and the velocity, and it's usually labelled with the letter :
The total momentum is the sum of the momentums. The initial situation is the following:
(it's not written explicitly, but I assume that the 5-kg object is still at the beginning).
So, at the beginning, the total momentum is
At the end, we have
(the mass obviously don't change, the new velocity of the 15-kg object is 1, and the velocity of the 5-kg object is unkown)
After the impact, the total momentum is
Since the momentum is preserved, the initial and final momentum must be the same. Set an equation between the initial and final momentum and solve it for , and you'll have the final velocity of the 5-kg object.