Answer:
C. 30.6m
Explanation:
To find the height of the tower, we are to use Newtons law of motion to solve this problem. Since the penny is falling from the top of the tower, it is acted by the acceleration due to gravity. The formula to be used is:

Where H is the height of the tower, t is the time taken to hit the ground, u is the initial velocity and g is the acceleration due to gravity.
Given that, t = 2.5 s, g =9.8 m/s², u = 0 m/s (at the top of tower)

Answer:
35870474.30504 m
Explanation:
r = Distance from the surface
T = Time period = 24 h
G = Gravitational constant = 6.67 × 10⁻¹¹ m³/kgs²
m = Mass of the Earth = 5.98 × 10²⁴ kg
Radius of Earth = 
The gravitational force will balance the centripetal force


From Kepler's law we have relation

Distance from the center of the Earth would be

The answer is to this question D
Answer:
proof in explanation
Explanation:
First, we will calculate the number of half-lives:

where,
n = no. of half-lives = ?
t = total time passed = 2100 million years
= half-life = 700 million years
Therefore,

Now, we will calculate the number of uranium nuclei left (
):

and the rest of the uranium nuclei will become thorium nuclei (
)

dividing both:

<u>Hence, it is proven that after 2100 million years there are seven times more thorium nuclei than uranium nuclei in the rock.</u>
Answer:It increases confidence because the more times you conduct the same experiment over and over should either prove your hypothesis right and wrong and eliminate any random occurrences that might affect your results.
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Explanation: