Answer:
Reflection involves a change in direction of waves when they bounce off a barrier. Refraction of waves involves a change in the direction of waves as they pass from one medium to another.
Rate of speed (3 m/s north is three miles per second north, so it's a rate of speed)
From the first law of thermodynamics, we use the equation expressed as:
ΔH = Q + W
where Q is the heat absorbed of the system and W is the work done.
We calculate as follows:
ΔH = Q + W
ΔH = 829 J + 690 J = 1519 J
Hope this answers the question. Have a nice day.
Theoretically, if the objects have the same mass and are moving towards each other at a speed of

, after a perfectly elastic collision, the object A is supposed to move with the same velocity in the opposite direction.
Answer:
The gravitational force between m₁ and m₂, is approximately 1.06789 × 10⁻⁶ N
Explanation:
The details of the given masses having gravitational attractive force between them are;
m₁ = 20 kg, r₁ = 10 cm = 0.1 m, m₂ = 50 kg, and r₂ = 15 cm = 0.15 m
The gravitational force between m₁ and m₂ is given by Newton's Law of gravitation as follows;

Where;
F = The gravitational force between m₁ and m₂
G = The universal gravitational constant = 6.67430 × 10⁻¹¹ N·m²/kg²
r₂ = 0.1 m + 0.15 m = 0.25 m
Therefore, we have;

The gravitational force between m₁ and m₂, F ≈ 1.06789 × 10⁻⁶ N