Answer:
a. friction
Explanation:
What is a common unbalanced force acting in motion? Common forces that are often unbalanced include the force of gravity and applied forces. When these forces are unbalanced, objects accelerate, change their position and find new configurations for which all forces are again balanced.
Friction is a kind of force.
Explanation:
I have a dog in my dog is a girl
Answer:
Relative motion of source and observer.
Explanation:
Doppler Effect : It is the change in the observed frequency of the wave due to<em><u> relative motion of the source and object </u></em>.