Answer:
1) 
2) 
3) 

Explanation:
Given:
width of river, 
speed of stream with respect to the ground, 
speed of the swimmer with respect to water, 
<u>Now the resultant of the two velocities perpendicular to each other:</u>



<u>Now the angle of the resultant velocity form the vertical:</u>



- Now the distance swam by the swimmer in this direction be d.
so,



Now the distance swept downward:



2)
On swimming 37° upstream:
<u>The velocity component of stream cancelled by the swimmer:</u>



<u>Now the net effective speed of stream sweeping the swimmer:</u>



<u>The component of swimmer's velocity heading directly towards the opposite bank:</u>



<u>Now the angle of the resultant velocity of the swimmer from the normal to the stream</u>:



- Now let the distance swam in this direction be d'.



<u>Now the distance swept downstream:</u>



3)
Time taken in crossing the rive in case 1:



Time taken in crossing the rive in case 2:



Systematic is just a certain way of doing something. So science being systematic may just refer to the scientific method or how theories are proved in science by repeating the scientific method over and over again.
When you say "heavy", you're talking about the gravitational force
between that object and another object, so it depends on what the
"other object" is.
If the "other object" is, let's say, the sun, then the gravitational attraction
between the Earth and sun is about 80 times as much as the gravitational
attraction between the Moon and sun, because the Earth has about 80 times
the mass of the Moon.
But if, somehow, the weight you have in mind is the gravitational attraction
between the Earth and the Moon, then those forces are equal. The force
of gravity between two objects depends on the product of both masses,
and it's equal in both directions.
If that isn't clear to you, let me give you this additional fact that's guaranteed
to knock you even further off-balance:
Your weight on the Earth is determined by the product of
(your mass) times (the Earth's mass).
The Earth's weight on you is determined by the product of
(your mass) times (the Earth's mass).
Your weight on Earth is the same as the Earth's weight on you.
Would you like to prove it ?
-- Turn the bathroom scale upside-down, so that the step-pad
is on the floor.
-- Then step on it, so that you're standing on the bottom, which
is facing up.
-- If you placed a little mirror on the floor, so that you can read
the numbers, which are facing down toward the floor, you'll
read your own weight, even though with the scale upside-down,
you're weighing the Earth on you.
Answer:
8 units
Explanation:
F=(k*q1*q2)/(r^2)
K is a constant, q1 is charge of 1, q2 is charge of 2, r is distance between the two.
Answer:
945 joules
Explanation:
Kinetic energy = 1/2(MV²)
Given parameters
Mass = 2.1kg
Velocity = 30m/s
K.E = 1/2(2.1 x 30²)
K.E = 1/2( 2.1 x 900)
K.E = 2.1 x 450
K.E = 945 joules