That was Johannes Kepler.
He couldn't say why that should happen. But he was able to show that
if we <em><u>assume</u></em> the the sun is in the center of the solar system, and <em><u>assume</u></em>
that the planets revolve around the sun in elliptical orbits, and <em><u>assume</u></em> that
the farther a planet is from the sun the longer it takes to orbit the sun, then
<em>that matches everything that we see the planets actually doing in the sky</em>.
Then Isaac Newton came along, and wrote down a short, simple formula
for the force of gravity. And then he showed that <u>IF</u> his formula for gravity
is correct, then the planets MUST do everything that we see them actually
doing in the sky, and they MUST behave according to Kepler's laws.
Wotta guy !
Answer:
(A) 374.4 J
(B) -332.8 J
(C) 0 J
(D) 41.6 J
(E) 351.8 J
Explanation:
weight of carton (w) = 128 N
angle of inclination (θ) = 30 degrees
force (f) = 72 N
distance (s) = 5.2 m
(A) calculate the work done by the rope
- work done = force x distance x cos θ
- since the rope is parallel to the ramp the angle between the rope and
the ramp θ will be 0
work done = 72 x 5.2 x cos 0
work done by the rope = 374.4 J
(B) calculate the work done by gravity
- the work done by gravity = weight of carton x distance x cos θ
- The weight of the carton = force exerted by the mass of the carton = m x g
- the angle between the force exerted by the weight of the carton and the ramp is 120 degrees.
work done by gravity = 128 x 5.2 x cos 120
work done by gravity = -332.8 J
(C) find the work done by the normal force acting on the ramp
- work done by the normal force = force x distance x cos θ
- the angle between the normal force and the ramp is 90 degrees
work done by the normal force = Fn x distance x cos θ
work done by the normal force = Fn x 5.2 x cos 90
work done by the normal force = Fn x 5.2 x 0
work done by the normal force = 0 J
(D) what is the net work done ?
- The net work done is the addition of the work done by the rope, gravitational force and the normal force
net work done = 374.4 - 332.8 + 0 = 41.6 J
(E) what is the work done by the rope when it is inclined at 50 degrees to the horizontal
- work done by the rope= force x distance x cos θ
- the angle of inclination will be 50 - 30 = 20 degrees, this is because the ramp is inclined at 30 degrees to the horizontal and the rope is inclined at 50 degrees to the horizontal and it is the angle of inclination of the rope with respect to the ramp we require to get the work done by the rope in pulling the carton on the ramp
work done = 72 x 5.2 x cos 20
work done = 351.8 J
Answer:
A) That man-made trade barriers are the biggest challenge facing Africa's international trade success.
Explanation:
Based on the discussion of high trade costs, the presence of numerous tariffs, and problems with customs procedures and duties it is clear that the author feels that man-made trade barriers are the biggest challenge facing Africa's international trade success.
1st Law Of Motion: An object will often remain at rest or continue moving unless acted upon.
2nd Law Of Motion: Force is equal to mass times acceleration
3rd Law Of Motion: For every action there is an equal or opposite reaction