Answer:
1.73 seconds
Explanation:
The velocity the ball first hits the ground with is:
v² = v₀² + 2aΔx
v² = (0 m/s)² + 2 (-10 m/s²) (-20 m)
v = -20 m/s
The velocity it rebounds with is 3/4 of that in the opposite direction, or 15 m/s.
The time it takes to return to the ground is:
Δx = v₀ t + ½ at²
0 = (15 m/s) t + ½ (-10 m/s²) t²
0 = t (15 − 5t²)
t = √3
t ≈ 1.73 seconds
Advantages of copper cables are that copper is an extremely powerful conductor of electricity and much more stable over time. It can withstand higher temperatures than aluminum and is more resistant to damage.
Disadvantages: Copper is more expensive and heavier and thus requires structural support.
Advantages of aluminum cables are that it is less expensive, easier to work with and light weight and so does not need structural support when strung over long distance.
Disadvantages: Aluminum is more susceptible to corrosion and requires periodic replacement. It needs much greater maintenance.
Advantages of steel cables are that steel does not rust, is fairly cheap and readily available. It has a higher tensile strength too.
Disadvantages: Steel cables are less ductile and are therefore more susceptible to fatigue.
They are both used to observe and describe matter.
