Answer:
When net force of zero acting on a ball which is at rest , then the object center of mass will not accelerate , but the object may begin to rotate .
Explanation:
Here when there is an object where several forces are acing upon are zero then the center of mass will not accelerate because we know that
Where acceleration of center of mass
= net force = 0
So the acceleration of center of mass will be zero
But the torque ,may not be zero as torque is product of individual force and perpendicular force .
Since if torque is not equal to zero then the object may begin to rotate
Answer:
Explanation:
We shall apply concept of Doppler's effect of apparent frequency to this problem . Here observer is moving sometimes towards and sometimes away from the source . When observer moves towards the source , apparent frequency is more than real frequency and when the observer moves away from the source , apparent frequency is less than real frequency . The apparent frequency depends upon velocity of observer . The formula for apparent frequency when observer is going away is as follows .
f = f₀ ( V - v₀ ) / V , f is apparent , f₀ is real frequency , V is velocity of sound and v is velocity of observer .
f will be lowest when v₀ is highest .
velocity of observer is highest when he is at the equilibrium position or at middle point .
So apparent frequency is lowest when observer is at the middle point and going away from the source while swinging to and from before the source of sound .