A valve is a flap of tissue that prevents blood from flowing back
Answer:
Mechanical
Explanation:
Electromagnetic waves are waves that have no medium to travel whereas mechanical waves need a medium for its transmission.
In rainforest sound travels faster because in the ocean sound travels very slow due to the pressure
Answer:
Work done W =1406.25 J
Explanation:
Work done on a body can be calculated using newton's 2nd laws:
F=ma
Hence acceleration of the block is given by:
Displacement of the object is given by:

Substitute the values
Now work done is given by:
W=F.S
W = 25×56.25
W =1406.25 J