Answer:
1) 3.92 J
2) 1596.08 J
3) 16.3 s ??
Explanation:
Initial Potential energy PE = mgh = 0.5(9.8)(0) = 0 J
Initial Kinetic energy KE = ½mv² = ½(0.5)80² = 1600 J
PE = 0.5(9.8)(0.80) = 3.92 J
KE = 1600 - 3.92 = 1596.08 J
Question 3 is not clear
to the point 80 cm above the ground the flight time is only 0.01 s
The time when the mass strikes ground again will be twice the time gravity takes to reduce the initial velocity to zero
t = 2(80.0 / 9.8) = 16.3 s
would not 80 m above the ground be a much more interesting point to consider?
PE = 0.5(9.8)(80) = 392 J
KE = 1600 - 392 = 1208 J
v₈₀ = √(2(1280) /0.5) = 69.5 m/s
t₈₀ = h/v(avg) = 80 / (½(80 + 69.5)) = 1.07 s
Answer:
6.13 s
219 N
Explanation:
Newton's law in the x direction:
∑F = ma
150 cos 30° N − 50 N = (30 kg) a
a = 2.66 m/s²
Δx = v₀ t + ½ at²
(50 m) = (0 m/s) t + ½ (2.66 m/s²) t²
t = 6.13 s
Newton's law in the y direction:
∑F = ma
Fn + 150 sin 30° N − (30 kg) (9.8 m/s²) = 0
Fn = 219 N
The moon is moving away from Earth at a rate of approximately 3.78 cm per year.
This migration of the Moon from the Earth is mainly due to the action of the Earth tides. It can be explained as follows:
- the Moon exerts a gravitational force on the Earth, which is stronger at the Equator (since the Equator is closer to the Moon), creating the tides
- However, the Earth rotates faster on its axis (one rotation every 24 hours) than the Moon (one rotation every 27 days), therefore the tidal bulge on Earth tries to pull the Moon "ahead" in its orbit. As a result, the Moon tends to sped up.
<span>- As opposite reaction, the Earth tends to slow down in its rotation, with a loss of angular momentum. Since the angular momentum must be conserved, the radius of the orbit of the Moon becomes larger, and this explains why the Moon is moving away from the Earth.</span>
Answer:
A) That man-made trade barriers are the biggest challenge facing Africa's international trade success.
Explanation:
Based on the discussion of high trade costs, the presence of numerous tariffs, and problems with customs procedures and duties it is clear that the author feels that man-made trade barriers are the biggest challenge facing Africa's international trade success.
