1. 168.1 Hz
To find the apparent frequency heard by the driver in the car, we can use the formula for the Doppler effect:
where
f is the original sound of the horn
v is the speed of sound
is the velocity of the observer (the driver and the car), which is positive if the observer is moving towards the source and negative if it is moving away
is the velocity of the sound source (the train), which is positive if the source is moving away from the observer and negative otherwise
In this problem we have, according to the sign convention used:
Substituting, we find:
2. 
The speed of light can be calculated as
where
d is the distance travelled
t is the time taken
In this problem:
is the total distance travelled by the laser beam (twice the distance between the Earth and the Moon)
t = 2.60 s is the time taken
Substituting in the formula,
Answer:
Support
Posture
Protection
Explanation:
Support – the skeleton keeps the body upright and provides a framework for muscle and tissue attachment.
Posture – the skeleton gives the correct shape to our body.
Protection – the bones of the skeleton protect the internal organs and reduce the risk of injury on impact.
This is a conservation of momentum problem! Here's how to do it:
Answer:
Regeneration means that an organism regrows a lost part, so that the original function is restored.
