Looking at decibel scale tables on internet, a "quiet whisper 1 meter away" is generally reported to have a sound intensity of about 20 dB, while a jackhammer 3 meters away produces a sound of about 100 dB of intensity, so option a) could be the correct one.
However, the other options could be considered correct as well, because without knowing the exact sound power produced by the whisper or by the jackhammer it's impossible to calculate the exact sound intensity with precision, and since the values reported in the three options are very similar, all the three of them can be considered as valid.
True
Variables is changing. It is any factor, trait or condition that can exist in differing amounts or types. An experiment has three types: Independent, Dependent and Controlled.
Answer:
The force needed to slow down the car is, F = 67.5 N
Explanation:
Given data,
The mass of the car, m = 15 kg
The initial velocity of the car, V = 60 m/s
The final velocity of the car, v = 15 m/s
The time period of deceleration, t = 10 s
The difference in the momentum of the car is,
mV - mv = 15(60 - 15)
= 675 kg m/s
The rate of change in momentum of the car gives the force acting on it.
F = (mV - mu) / t
Substituting the values,
F = 675 / 10
= 67.5 N
Hence, the force needed to slow down the car is, F = 67.5 N
<span>Most objects tend to contain the same numbers of positive and negative charge because this is the most stable situation. In fact, if an object has an excess of positive charge, it tends to attract an equal number of negative charges to balance this effect and restore neutrality: the attracted negative charges combine with the excess of positive charges, leaving the object electrically neutral.</span>
An evidence for the mammal competition hypothesis are the fossil records.
A gradual decline in the number of dinosaur species would likely mirror an equally gradual cause of their ultimate extinction. Conversely, a sudden "now you see them, now you don't" end to the dinosaurs implies a catastrophic cause. Depending on location and interpretation, the fossil record seems to say different things.
While mammals certainly prospered on the heels of the dinosaur extinction, it is unclear whether mammals and dinosaurs experienced little competition or if they regularly challenged each other for limited resources.