<span>The force of static friction F equals the coefficient of friction u times the normal force N the object exerts on the surface: F = uN. N is the centripetal force of the wall on the people; N = ma_N, where m is the mass of the people and a_N is the centripetal acceleration.
The people will not slip down if F is greater than the force of gravitation: F = uma_N > mg, or u > g/a_N.
a_N is the velocity v of the people squared divided by the radius of the room r: a_N = v^2/r.
The circumference of the room is 2 pi r = 28.3 m. So v = 28.3 * 0.8 m/sec = 22.6 m/sec.
So a_N = 114 m/sec^2.
g = 9.81 m/sec^2, so u must be at least 9.81/114 = 0.086.</span>
Let be the height of the building and thus the initial height of the ball. The ball's altitude at time is given by
where is the acceleration due to gravity.
The ball reaches the ground when after . Solve for :
so the building is about 16 m tall (keeping track of significant digits).
Answer: One of the signs a chemical reaction is taking place is the presence of bubbles. :)
Acceleration = (change in speed) / (time for the change)
= (49 m/s) / (5 seconds)
= (49 / 5) m/s / s
= 9.8 m/s²