Oil is a powerful source of energy used for cars, machines, and many other purposes. While studying sources of energy that could replace the use of oil, a student thinks about solar power, wind power, nuclear power, and electric batteries. The students asks,"Which type of source will waste the least energy and provide the most energy in all situations?" Which best describes why a scientist would ask a different question than this one?

A- The question asks about subjective personal preferences regarding energy.
B- The question focuses on the objective measurements of amounts of energy.
C- The question has too wide of a focus, as though all situations can be studied at once.
D- The question is focused on the future and finding new answers about changing needs.

insects!

explanation:

the area between the graph and the t axis

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.