Answer
given,
frequency from Police car= 1240 Hz
frequency of sound after return = 1275 Hz
Calculating the speed of the car = ?
Using Doppler's effect formula
Frequency received by the other car
..........(1)
u is the speed of sound = 340 m/s
v is the speed of the car
Frequency of the police car received

now, inserting the value of equation (1)


1.02822(340 - v) = 340 + v
2.02822 v = 340 x 0.028822
2.02822 v = 9.799
v = 4.83 m/s
hence, the speed of the car is equal to v = 4.83 m/s
Answer:to prevent serious damage when an accident occur
Explanation:to prevent serious damage when accident occur
Answer:
t = 4.28 s
Explanation:
The horizontal speed of a marble = 7 m/s
The horizontal displacement covered by the marble = 30 m
We need to find the time for which the marble is in air. Let the time is t. Using the formula for speed to find it as follows :

So, it will in the air for 4.28 s.
Answer:
a. 
b. 
Explanation:
Given:



The runner force average to find given the equations
a.




b.
Work done by the system by this force so




