Why does the frequency of a siren get higher as an ambulance using that siren gets closer?

An object thrown vertically upward from the surface of a celestial body at a velocity of 36 m/s reaches a height of sequalsminus0.9tsquaredplus36t meters in t seconds. a. determine the velocity v of the object after t seconds. b. when does the object reach its highest point? c. what is the height of the object at the highest point? d. when does the object strike the ground? e. with what velocity does the object strike the ground? f. on what intervals is the speed increasing?

According to newton’s first law of motion, which force is expected to cause a body to accelerate?

Find v(t), given acceleration a(t)=7j and initial velocity v(0)=k