Answer:
Terminal velocity of object = 12.58 m/s
Explanation:
We know that the terminal velocity is attained when drag force and gravitational force are of the same magnitude.
Gravitational force = mg = 80 * 9.8 = 784 N
Drag force = 
Equating both, we have
So v = 12.58 m/s or v = -15.58 m/s ( not possible)
So terminal velocity of object = 12.58 m/s
The correct option is A.
In physics, inertia has to do with Newton's first law of motion which states that an object will continue in its state of rest or in motion unless it is acted upon by a force. Thus, inertia refers to the tendency of an object to continue its motion in a straight line at constant velocity. In the question given above, the car that its brake failed would have continue moving indefinitely if it did not crash into another car, that is, it will continue in its state of motion.
F=ma
Velocity is Distance over time so Vf = 75/15 = 5m/s
Find acceleration V=Vo+at. plugging in the values you know, you get
0.33m/s^2
F=(2100)(0.33)=693N
Use of fossil fuels has not lead to increased use of wood as heat source.
Answer: Option D
<u>Explanation:</u>
Fossil fuels are materials required to generate heat or thermal energy and they are obtained by the decomposed remains of plants, animals and human beings. But the fossil fuels generally present in the bottom layer of earth crust or sometimes mixed with stones or rock minerals. So we need to highly energetic drilling devices to extract the fossil fuels.
Thus, before the introduction of fossil fuels, wood is used as the igniting source for heat energy. But the entry of fossil fuels have reduced the use of wood as igniting source in cooking, burning etc.
Thus, the use of fossil fuels have increased exchange of culture and ideas as fuels are mostly imported from other nations, it lead to development of faster transportation methods and increased the availability of products including heat, plastics and medicine. But similarly, the use of fossil fuels have not increased the use of wood as heat source, instead it decreased the use of wood as heat source.
