Answer:
The time taken by the rock to reach the ground is 0.569 seconds.
Explanation:
Given that,
A student throws a rock horizontally off a 5.0 m tall building, s = 5 m
The initial speed of the rock, u = 6 m/s
We need to find the time taken by the rock to reach the ground. Using second equation of motion to find it. We get :

So, the time taken by the rock to reach the ground is 0.569 seconds. Hence, this is the required solution.
90% of stars in the solar system are main sequence stars.
Given:
500 containers ; 5 of these are defective.
A = event that 1st is defective = 5/500
B = event that 2nd is defective = 4/499
C = event that 3rd is defective = 3/498
a) 4/499
b) 5/500 * 4/499 = 20/249,500 = 1/12,475
c) 495/500 * 494/500 = 244,530 / 250,000 = 24,453/25,000
d) 5/500 * 4/499 * 3/498 = 60/124,251,000 = 1/2,070,850
Explanation:
Given that,
The disintegration constant of the nuclide, 
(a) The half life of this nuclide is given by :



(b) The decay equation of any radioactive nuclide is given by :


Number of remaining sample in 4.44 half lives is :


So, 

(c) Number of remaining sample in 14.6 days is :


So, 

Hence, this is the required solution.