Answer: observed frequency (f') = 511.97Hz
Explanation: when there is a relative motion between an observer and a sound source, the frequency of sound wave perceived by the observer is different from the frequency of originally sent out by the sound source.
This is called Doppler effect and given mathematically below as
f' = (v + v') /(v- vs) * f
f' = observed frequency
v = speed of sound in air = 340m/s
v' = velocity of observer= 45m/s
vs = velocity of source relative to observer = - 36m/s ( the negative sign came as a result of the fact that the velocity of the source is in opposite direction to the velocity of the observer)
f = original frequency of sound source = 500Hz
f' = (340 + 45)/{340 -(-36)} * 500
f' = 385/ (340 + 36) * 500
f' = 385/ 376 * 500
f' = 1.0239 * 500
f' = 511.97Hz
A baseball bat hits a ball is an example of contact force.
Option A.
<h3><u>Explanation:</u></h3>
Contact force is defined as those forces which are acting between two bodies by actually touch between two bodies.
In case of the book falling to ground, the force acting is the gravitational force. Gravitational force acts even when two bodies aren't in contact. So its a non contact force.
Similar is the condition of the leaf and ground where the gravitational force acts.
The magnetic force between the paper clip and the magnet is also non contact force, which acts even when two bodies aren't in contact.
But the bat hitting the ball is having direct contact between the two bodies, and their contact is what makes the ball fly off. So its a contact force.
Formula: PE = mgh
m = 20 kg, g = 9.8 m/s^2 h= ?
1000 = 20 * 9.8 * h
1000 = 196h
h = 5.10204082
The height is around 5m
