The law of energy conservation states that energy cannot be created or destroyed, so choices B to D are immediately invalid. Choice A can explain this occurrence: <u>A. Some of the energy is used to combat friction, and thus is transformed from mechanical energy to heat.</u>
Answer:
reflection is the act of reflecting or the state of being reflected while echo is
reflection of sound waves from a surface back to the initial listener
Answer:
1. 218.55 N
2. 
3. 
Explanation:
Part 1;
Net force
where m is mass, g is gravitational force and
is the angle of inclination

Frictional force,
is given by
where
is the coefficient of static friction


Since
, therefore, the block doesn’t slip and the frictional force acting is mgh=218.55N
Part 2.
Using the relationship that
Frictional force 



The maximum angle of inclination 

Part 3:
Net force on the object is given by
where
is the coefficient of kinetic friction

= 9.8 ( sin 38 - (0.51) cos 38 )
= 
Answer:
<h3> B. 4 m/s</h3>
Explanation:
The formula for Speed is distance per time.
<h3>Therefore Speed = Distance / Time</h3>
<u>Data</u>
D = 40 m
T = 10 sec
S = ?
<h3> Speed = 40m /10sec</h3>
To find the speed , divide the distance by the time.
Note : the unit for Speed is meter /second
<h3> Speed = 4 m/s</h3>
Therefore the speed of the wave, the surfer is riding on is 4 m/s.