The three branches of science are life, earth, and physical science.
Life science deals with living organisms, so, biology is the most important of these sciences, although there are many.
Earth science deals with Planet Earth, studying its atmosphere, lithosphere, etc.
Physical science studies the inorganic world.
Answer:
Natural science is concerned with the description, prediction, and understanding of natural phenomena based on empirical evidence from observation and experimentation. It can be divided into two main branches: life science (or biological science) and physical science.
Explanation:
a) since force = mass * acceleration
f= 900 * 0 (because constant speed = 0 acceleration)
similarly b) f = 0
Velocity of swimmer across river = 1.30 m/s
Distance arrived downstream = 48 m
Width of river = 64 m
Time taken to cross river = 
= 
Speed of river current = 
= 
So, the river is flowing at a speed 0.975 m/s.
