An object is thrown horizontally from the open
window of a building. If the initial speed of the
object is 20 m/s and it hits the ground 2.0 s later,
from what height was it thrown? (Neglect air
resistance and assume the ground is level.)
Initial vertical velocity = 0
formula: s = ut + (1/2)*g*t^2
s = 0 + 1/2*9.8*2^2
s = 9.8*2 = 19.6 m
Answer:
d
He could pull the mass down farther.
Well, i would tell the kid that light is electromagnetic radiation which
is visible. The frequency and wavelength is just right so the radiation
becomes visible, and that visible radiation goes away from the star and
reaches earth
It also depends on the age of the child and the comprehension level
At critical temperature, the resistivity of the superconductor
B. It suddenly drops to zero
Explanation:
Materials can be classified into three different types depending on their resistance:
- Conductors: these materials have generally low resistance and allow electricity to pass through easily. The resistance of a conductor increases linearly with the temperature
- Insulators: these materials do not allow electricity to pass through - so they have very high resistance
- Semi-conductors: these are materials that are insulators are room temperature, however they becomes conductors when heated. Therefore, the resistance of a semiconductor decreases when the temperature increases
- Superconductors: these are special materials that are normally conductors; however, at very low temperatures (we are talking about temperature very near to 0 K), their resistance becomes suddenly zero.
Therefore, the correct answer is:
B. It suddenly drops to zero
Learn more about current and resistance:
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All frequencies of light in hertz are in between
and
Light with a lower frequency than 4 * 10^14 Hz, are called infrared and can't be seen by human eye. Light with a higher frequency than 8 * 10^14 Hz, are called ultraviolet and can't bee seen by human eye.
Therefore, the maximum frequency of visible light in Hz, is
8 * 10^14 Hz
