Answer:
The total energy stays the same but is converted from being stored as gravitational potential energy into kinetic energy of the car as it moves.
Explanation:
the law of conservation of energy states that the total energy of an isolated system remains constant, and since it is gaining speed that energy will be kinetic
The answer is either
b A system in which Newton's Laws are valid
or
c A system in which there are no external forces.
Explanation:
not a, and not d
There are energy changes in a closed system.
A closed system obeys the conservation laws in its physical description.
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: 586.60N/m
Explanation:
In this scenario, the elastic potential energy of the spring is converted into potential energy.
0.5*K*x^2 = mgh
Thus K = 2mgh/x^2
=(2*2.90*10^-2*9.8*7.23)/(8.37*10^-2)^2
=586.599
Therefore K = 586.60N/m
