Actually Welcome to the Concept of the Force and Power.
Since, according to the Newton's law,
Force = mass * Acceleration.
hence, here
Force = 142 N, accelration = 22.75 m/s2
hence, mass = 142/22.75
===> Mass = 6.24 Kg
hence the mass of the shot is 6.24 Kg
As the question is about changing in frequency of a wave for an observer who is moving relative to the wave source, the concept that should come to our minds is "
Doppler's effect."
Now the general formula of the Doppler's effect is:
-- (A)
Note: We do not need to worry about the signs, as everything is moving towards each other. If something/somebody were moving away, we would have the negative sign. However, in this problem it is not the issue.
Where,
g = Speed of sound = 340m/s.
= Velocity of the receiver/observer relative to the medium = ?.
= Velocity of the source with respect to medium = 0 m/s.
= Frequency emitted from source = 400 Hz.
= Observed frequency = 408Hz.
Plug-in the above values in the equation (A), you would get:
Solving above would give you,
= 6.8 m/s
The correct answer = 6.8m/s
If it is a multiple choice question is C. Infrared waves do not carry enough energy to kill cancerous cells.
a) 6.25 rad/s
The law of conservation of angular momentum states that the angular momentum must be conserved.
The angular momentum is given by:
where
I is the moment of inertia
is the angular speed
Since the angular momentum must be conserved, we can write
where we have
is the initial moment of inertia
is the initial angular speed
is the final moment of inertia
is the final angular speed
Solving for , we find
b) 28.1 J and 35.2 J
The rotational kinetic energy is given by
where
I is the moment of inertia
is the angular speed
Applying the formula, we have:
- Initial kinetic energy:
- Final kinetic energy:
