Why roads at mountains are serpentine?

This is to reduce the effort. It follows the principle of a screw which in turn is a modified form of inclined plane.

See the pic on left. Though we have to do a greater work (against friction) the average force or effort is less and the risk or danger of accident is less.

Human-powered aircraft require a pilot to pedal, as in a bicycle, and produce a
sustained power output of about 0.30 hp.

The Gossamer Albatross flew across the English Channel on June 12, 1979, in 2h 49 min.

(a) How much energy did the pilot expend during the flight?

(b) How many Snickers candy bars (280 Cal per bar) would the pilot have to consume to be “fueled up” for the flight?

[Note: The nutritional calorie, 1Cal, is equivalent to 1000 calories (1000 cal) as defined in physics. In addition, the conversion factor between calories and joules is as follows: 1Cal = 1000 cal = 1 kcal = 4186 J. ]

A rock is thrown vertically upward from the ground with an initial speed 15m/s.

a. how high does it go
b. how much time is required for the rock to reach its maximum height?
c. what is the rock’s height at t=2.00s?

(Posted by Merhawi)

Answer:

(a)

u=15m/s

a=-10m/s²

v=0 m/s (at the max height)

S=?

v²-u²=2aS

S=v²-u²/2a

=225/20

=11.25 m

(b) From the above case

using v=u+at

t=v-u/a=1.5s

(c) Use S = ut + 1/2 at²

put t=2s, u = 15m/s, a=-10m/s²

S=30 – 20 = 10 m

(If you use g = 9.8 m/s² The answers will be slightly different)