having to push a rough and heavy box across the floor to move it
Explanation:
Friction is not a useful force because we have to exert even more force to push a body that is rough and heavy across the floor to move it.
- Frictional force is a force that opposes the motion of a body.
- It costs more and uses more energy to push a rough and heavy box on surface because of friction.
- This wastes energy in systems that deals with pushing.
Friction is useful in that:
- the heat energy produced when two surfaces rub together is very useful.
- the friction between your feet and the floor keeping you from slipping and makes walking possible.
- the tread on tires helping the moving vehicle slow down and stop when necessary.
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The correct answer for the question that is being presented above is this one: "<span>c. Planets orbit in elliptical patterns; a planet's orbit covers equal areas in equal amounts of time; planets' orbits are shorter or longer depending on their distance from the Sun."</span>
Here are the following choices:
a. Planets orbit in elliptical patterns; the bigger the planet, the more gravitational pull; a planet's gravitational pull is stronger or weaker depending on its distance from the Sun.
b. A planet's orbit covers equal distances in equal amounts of time; the speed of a planet's orbit depends on its distance from the Sun; the bigger the planet, the slower it moves.
c. Planets orbit in elliptical patterns; a planet's orbit covers equal areas in equal amounts of time; planets' orbits are shorter or longer depending on their distance from the Sun.
Answer:
3.036×10⁻¹⁰ N
Explanation:
From newton's law of universal gravitation,
F = Gm1m2/r² .............................. Equation 1
Where F = Gravitational force between the balls, m1 = mass of the first ball, m2 = mass of the second ball, r = distance between their centers.
G = gravitational constant
Given: m1 = 7.9 kg, m2 = 6.1 kg, r = 2.0 m, G = 6.67×10⁻¹¹ Nm²/C²
Substituting into equation 1
F = 6.67×10⁻¹¹×7.9×6.1/2²
F = 321.427×10⁻¹¹/4
F = 30.36×10⁻¹¹
F = 3.036×10⁻¹⁰ N
Hence the force between the balls = 3.036×10⁻¹⁰ N
Answer:
b . Move the conductor near a magnet
