Use this formula for an object starting from rest and accelerating:
Distance = (1/2) (acceleration) (time)²
In this problem, the distance is 40 meters, and acceleration is gravity.
So . . .
40 m = (1/2) (9.8 m/s²) (time)²
Divide each side by (4.9 m/s²) :
time² = (40 m) / (4.9 m/s²)
time² = 8.16 sec²
Take the square root of each side :
√(time²) = √(8.16 sec²)
time = 2.86 seconds
Round it to 2.9 sec <em>(choice B)</em>
Complete Question
The complete question is shown on the first uploaded image
Answer:
The answer is a
Explanation:
The explanation is shown on the second uploaded image
Answer: Radio signals sent through space
Explanation:
>Radio signals are electromagnetic signals which can travel through space even in vacuum where no air is absent . Radio signals carry energy in the form of electromagnetic wave .
>Thunder heard from many miles away is due to propagation of sound wave in the air or atmosphere . The sound wave carries energy in the form of mechanical energy which can not propagate in vacuum and requires a medium .
>When nuclei of atoms split into parts they fly away from each other with some speed carrying kinetic energy which is a part of mechanical energy .
Thus mechanical energy is involved in all the given examples expect the case of radio signals sent through space.
In his celebrated Second Law of Motion, Newton wrote:
Net force = (mass) x (acceleration).
By the process of "plugging in numbers", we can write
1255 N = (41 kg) x (acceleration)
Now, after dividing each side by (41 kg), we have
(1255 N) / (41 kg) = acceleration.
But (1255N)/(41kg) = 30.61 m/s² .
So unless we have carelessly blooped the calculations somewhere,
that 30.61 m/s² is the answer we're looking for.
The answer is A. Cones, as rods are not sensitive to color. :)