ElectricPavlov

Yes it is theoretical in that friction is ignored.....but GRAVITY is used in the equation  ( the 'g'  in 'mgh' )  

Power is  Joules per second (watts)

Power = j/s = 50/100,000 = .0005 watts    (not much)

Generally, algabraic expressions have a VARIABLE   (often denoted as 'x') and we simplify them in order to solve for 'x'...that is ...find the value of 'x'  .....

Skateboarder's Kinetic Energy = 1/2 mv^2     all of this energy is converted to POTENTIAL ENERGY =mgh   (since there is no friction involved)

1/2mv^2 = mgh      the m's 'cancel and you are left with:

1/2 v^2 = gh           Substitute and solve for 'h'

1/2 (5.25)^2 = 9.81(h)

h= 1.40 meters high

$10.50 / 3 pizzas    x  10 pizzas  = 35 dollars

Why don't you just use the calculator to determine this ????

60.95 degrees

THAT is just a solid  horizontal line at y= 4   on the coordinate plane.....count up 4 units from the horizontal axis and draw a solid horizontal line.....

2 1/2 = 5/2

5/2  / 2  =  5/2 /  2/1  = 5/2 x 1/2 = 5/4 = 1 1/4

F=ma

the force DOWN the plane (parallel with surface) =  1380 (9.81) sin 11 = 2583.13 N

F=ma

2583.13 N = 1380 kg  (a)

a=1.872 m/s^2

x = xo +vot + 1/2 a t^2       And realize   xo = 0  vo = 0

x= 28m = 1/2 (1.872) t^2

t = 5.47 sec

vf= at = 1.872 (5.47) = 10.24 m/s

Hope I didn't make a mistake!

mgh = potential energy = 1380 (9.81)28 sin11= 72327.75J

  As a check (and a simpler method) the POTENTIAL energy is converted to KINETIC energy at the bottom of the incline

  Kinetic energy = 1/2mv^2         Potential energy = kinetic energy

72327.75 = 1/2 (1380) v^2       v= 10.24 m/s    Which agrees with what we found (the long way) above !

There are 2.54 cm to the inch     7.5 inches  x  2.54 cm/inch = 19.05 cm = DIAMETER

Radius = 1/2 Diameter = 9.525 cm

Area = pi x r^2 = pi x (9.525)^2 = 285 cm^2  (three sig fig)