I hope this helps you out!
Speed of ball is 19.80 m/s .
<u>Explanation:</u>
We have , a 2.0 kg ball is resting at the top of a 20 m hill. if the ball rolls down the entire hill,We need to find how fast will it be going.Let's find out:
We know that,
Potential energy : This is the energy possessed by an object due to it's virtue of height and is given by 
, where m is mass , g is acceleration due to gravity & h is height !
Kinetic energy : This is the energy possessed by an object due to it's virtue of motion and is given by 
, where m is mass & v is the velocity of object !
By conservation of energy :
⇒ 
⇒ 
⇒ 
According to question , h=20 m i.e.
⇒ 
⇒ 
⇒ 
Hence , Speed of ball is 19.80 m/s .
Subatomic particles cannot be broken down any further
Physics is known as the fundamentals of science, as all the branches of science, whether it is biology, chemistry, ecology, botany, environmental science, geology, geography, and more all follow the laws of physics, such as laws of thermodynamics, etc. Chemistry is existent because of physics due to the Conservation of mass. Once you get to a much deeper level of science, you will notice that all the fields of science start to blend together and all add up to one huge painting!
f' = frequency observed by the police car after sound reflected from the vehicle and comes back to police car = 1250 Hz
f = frequency emitted by the police car = 1200 Hz
V = speed of sound = 340 m/s
v = speed of vehicle = ?
frequency observed by the police car is given as
f' = f (V + v)/(V - v)
inserting the values in the above equation
1250 = 1200 (340 + v)/(340 - v)
v = 6.9 m/s
