Answer:
Refraction is the slowing down of light waves as they pass into a different medium and speeding as they pass out.
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Answer:
Speed of the ball relative to the boys: 25 km/h
Speed of the ball relative to a stationary observer: 35 km/h
Explanation:
The RV is travelling at a velocity of

Here we have taken the direction of motion of the RV as positive direction.
The boy sitting near the driver throws the ball back with speed of 25 km/h, so the velocity of the ball in the reference frame of the RV is

with negative sign since it is travelling in the opposite direction relative to the RV. Therefore, this is the velocity measured by every observer in the reference frame of the RV: so the speed measured by the boys is
v = 25 km/h
Instead, a stationary observer outside the RV measures a velocity of the ball given by the algebraic sum of the two velocities:
v = +60 km/h + (-25 km/h) = +35 km/h
So, he/she measures a speed of 35 km/h.
Reaction force/support force/ lift/ buoyancy/ weight depends on situation
1). Work = (force) x (distance)
Work = (3,000 newtons) x (35 meters) = 105,000 newton-meters = <em>105,000 joules</em>
2). Power = (work) / (time)
Power = (105,000 joules) / (90 seconds)
= 1,166-2/3 joules per second =<em> 1,166 and 2/3 watts</em> .
<em>Note:</em>
That's no ordinary man.
1,166 watts is the same as roughly 1.6 horsepower.
Not too many people can sustain 1 horsepower or more for 90 seconds.
The correct answer is
<span>C) Amount of heat absorbed or released is doubled if quantity is doubled. If a different substance with half the specific heat capacity is used, the amount of heat absorbed or released is cut in half.
In fact, the amount of heat released or absorbed is given by:
</span>

<span>where
m is the mass of the substance
Cs is the specific heat capacity of the material
</span>

is the change in temperature
<span>
We can see that Q is directly proportional to both m (mass, or quantity of the substance) and Cs (specific heat capacity). So if the quantity (m) is doubled, the amount of heat (Q) is doubled as well. Similarly, if the specific heat capacity (Cs) is cut in half, the amount of heat (Q) is cut in half as well.</span>