As per Newton's II law we know that

here F = force applied
m = mass of object = 2 kg
a = acceleration = 2 m/s^2
now as per above formula we will have


so here applied force on the ball will be 4 N
Answer:
For example, when you jump, your legs apply a force to the ground, and the ground applies and equal and opposite reaction force that propels you into the air. Engineers apply Newton's third law when designing rockets and other projectile devices.
Explanation:
These 255.75 Hz and 256.25 Hz sounds can be thought of as a sum of two waves with frequencies.
Answer: Option A
<u>Explanation:</u>
To solve this, it is necessary to take into account the concepts related to frequency and period, and how they are related to each other.
Let frequency of beat = f
The relationship that defines both agreements is given by the equation,

Then the frequency for the previous period given (2sec) is

The beat frequency of two frequencies is equal to the difference between the two frequencies, then


Hence, Option A is correct.
Similarly we can check like these for other options too as below,
For option B,
.
For Option C, 
For Option D, 
For Option E, 
Therefore, the sum of the frequencies in the sound wave would be 256.25Hz and 255.75Hz.
Answer:
You are driving at Vo= 15.2 m/s = 54.72 km/h
Explanation:
Δf= 72.1 Hz
f= 813 Hz
v= 343 m/s
Δf= f* [ (v-(-vo) / v) - ( v-(vo) / v) ]
clearing vo:
Vo= 15.2 m/s