Answer:
A) must equal angle of reflection
Explanation:
"The angle of incidence is equal to the angle of reflection". This is true according to the first law of reflection. For this to be totally true, the plane surface in consideration must be a smooth surface. Since it is a law, it cannot be changed because it has been proved to be true.
Note that the angle of incidence is the angle between the incidence ray and the normal ray(this ray is perpendicular to the surface) while the angle of reflection is the angle between the reflected ray and the normal.
The gravitational force between two objects is given by:
F = GMm/r²
F = force, G = gravitational constant, M and m are the masses, r = distance between the objects.
The force is dependent on only the masses of the objects and the distance between them. It is not dependent on the temperature of the objects.
Choice B
A. a lever
Explanation:
To remove a nail from wood, a lever will be the best machine to use. In a lever, effort is applied to move a large load. The nail is treated as the load.
- Most hammers have nail removers that can be used to pull out nails.
- The force is applied at the handle.
- The head of the hammer has a fulcrum and nail remover part where the load is.
- This gives a large mechanical advantage and the nail can be pulled out.
- Wedge, wheel and axle and movable pulley are not machines that works as nail removers.
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Heat used by electric heater :
Q = m • c • ∆T
Q = (75 kg)(4200 J/kg°C)(43°C - 15°C)
Q = 8.82 × 10⁶ J
Cost of electrical energy :
Cost = (8.82 × 10⁶ J)/(3.6 × 10⁶ J) • ($ 0.15)
Cost = $ 0.3675