Physics problem. please help.?
Spot the Wonder Cow has strapped on
her roller blades and rocket pack and is
standing at the bottom of a hill inclined
at 20.° to the horizontal. If Spot's rocket
pack provides a force of 2.0 X 103 N and
Spot has a mass of 250 kg, how long will
it take her to reach the top of a 250-mlong
hill?
Update:txt answer: 17s
Comments
Neglecting friction:
Fɴeт = m • a
Fappʟied – m • g • sin[θ] = m • a
(2 ×10³) – (250) • (9.8) • sin[20°] = (250) • a
2000 – 838 = (250) • a
a = 4.65 m/sec² up the ramp
Dʀaмp = (½) • a • t² + (Vi) • t ... initial velocity = Vi = 0
250 = (½) • (4.65) • t²
t = 10.4 sec
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
... If you meant a 250 m HIGH hill then the length traveled is
Ramp Length = 250 ⁄ sin[20°] = 731 meters ... and ...
Dʀaмp = (½) • a • t²
731 = (½) • (4.65) • t²
t = 17.7 sec
Gravity force on Spot Fg = m*g*sinÎ = 837.95 N
Net force up the hill Fn = Fr - Fg = 2000 - 837.95 = 1162.05 N
a = Fn/m = 1162.05/250 = 4.65 m/s²
t = â[2s/a] = â[2*250/4.65] = 10.37 sec
This IS the correct answer assuming there's no friction involved.......
Good catch, bonobo!