Asled plus passenger with total mass m = 52.3 kg is pulled a distance d = 21.8 m across a horizontal, snow-packed surface for which the coefficient of kinetic friction with the sled is μk = 0.13. the pulling force is constant and makes an angle of φ = 36.7 degrees above horizontal. the sled moves at constant velocity. a) write an expression for the work done by the pulling force in terms of m, g (acceleration due to gravity), φ, μk, and d. b) what is the work done by the pulling force, in joules? c) write an expression for the work done on the sled by friction in terms of m, g (acceleration due to gravity), φ, μk, and d. d) what is the work done on the sled by friction, in joules?

Explanation:

Since the sled plus passenger moves with constant velocity , force applied will be equal to frictional force. Let the force applied be F

a ) Frictional force = μ R = F cosφ

R = mg - F sinφ

μ(mg - F sinφ)  = F cosφ

μmg = F (μsinφ+cosφ)

F = μmg / (μsinφ+cosφ)

Work done

= F cosφ x d

= μmg x cosφ x d / (μsinφ+cosφ)

b )Work done

= 0.13 x 52.3 x 9.8 cos36.7 x 21.8 / ( 0.13 sin36.7 +cos36.7)

= 1164.61 / .87946

1324.23 J

c ) work done on the sled by friction

= - (work done by force)

= - μmg x cosφ x d / (μsinφ+cosφ)

d ) work done on the sled by friction

= - 1324.23 J

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )