Answer : The correct option is (d) 2.73 m
Explanation :
By the 2nd equation of motion,
where,
s = distance or height = ?
u = initial velocity = 3.0 m/s
t = time = 0.5 s
a = acceleration due to gravity =
Now put all the given values in the above equation, we get:
Therefore, the correct option is (d) 2.73 m
Answers:
a) 5400000 J
b) 45.92 m
Explanation:
a) The kinetic energy of an object is given by:
Where:
is the mass of the train
is the speed of the train
Solving the equation:
This is the train's kinetic energy at its top speed
b) Now, according to the Conservation of Energy Law, the total initial energy is equal to the total final energy:
Where:
is the train's initial kinetic energy
is the train's initial potential energy
is the train's final kinetic energy
is the train's final potential energy, where
is the acceleration due gravity and
is the height.
Rewriting the equation with the given values:
Finding :
Answer: The frequency heard will be f = 275.675Hz
Explanation: When an object emitting sound is moving, it occurs a phenomenon called Doppler shift or Doppler effect. What happens is that the sound gets higher when the moving object comes closer the observer and becomes lower after it passes, This change is due to the quantity of waves that passes through an area in an unit of time.
The formula to calculate the Doppler effect is as follows
f = () · f₀
f is the observed frequency;
c is the speed of sound;
Vs is velocity of the source;
f₀ is the emitted frequency of source;
Substituting and calculating,
f = · 300
f = 275.675 Hz
Thus, the frequency heard by the police officer is 275.675Hz.