1 hour = 3,600 seconds
1 km = 1,000 meters
75 km/hour = (75,000/3,600) m/s = 20-5/6 m/s
The mean speed during the deceleration is
(1/2)(20-5/6 + 0) = 10-5/12 m/s.
Traveling at this average speed for 21 seconds,
the bus covers
(10-5/12) × (21) = 218.75 meters.
At time 
, the ball's horizontal and vertical velocities can be represented as
However, since the ball is thrown horizontally, we have 
. The horizontal and vertical positions at time are
The ball travels a distance of 22 m horizontally from the throw point, thus
With this, we determine that the time for the ball to reach the ground is
When it touches down, 
and
Answer:
Stars generate energy by the process of nuclear fusion.
They are large entities composed of gaseous elements.
The main constituents of stars are hydrogen and helium.
Explanation:
Stars are colossal objects with extensive gravitational forces causing them to contract, which allows fusion to take place: the atomic nuclei in the star's core are drawn very close together due to gravity and elevated temperatures, leading to the fusion reaction. This fusion serves as the energy output for a star.
Conversely, it is true that stars predominantly consist of hydrogen and helium (two hydrogen nuclei can fuse to become helium), which implies that a star is essentially an enormous ball of gas without a solid surface suitable for standing on.
As for the presence of water on a star, it is simply impossible. The extreme temperatures found in stars are far too high for water to exist in any liquid state on their surfaces.
1) The initial velocity is zero. 2) We consider the downward direction as positive.
3) h = 25.66 m.
Explanation:
This is a problem of free fall.
1) In free fall, the initial velocity starts at zero, and acceleration remains constant throughout, equal to gravity.
2) It's common to choose downward as the positive direction.
3) For the latter part of the fall:
y₀ - y = h/2 when t = 1 s,
y = y₀ + v₁ t + ½ g t²,
with v₁ being the initial velocity at height h / 2,
v₁ t = (y - y₀) - ½ g t².
v₁ = h / 2 - ½ g t².
Now, let's set up the first interval equation:
v₁² = v₀² + 2 g (y₁ - y₀).
Since in this case v₀ = 0,
v₁² = 2 g (y₁ - y₀) = 2g h/2.
Next, our equations become:
v₁² = (h/2 - g/2)² and v₁² = (2g h / 2).
Thus, solving the quadratic equation leads to:
h² - 3 g h + g² = 0, which simplifies to h² - 29.4 h + 96.04 = 0.
Finally, solving this yields h = 25.66 m as the height.
