A student who weighs 552 N climbs a stairway (vertical height of 3.5 m) in 20 s. (a) How much work is done? (b) What is the power output of the student?

A crate with a mass of 35.0 kg is pushed with a horizontal force of 150 N. The crate moves at a constant speed across a level, rough surface a distance of 5.30 m. (a) What is the work done (in J) by the 150 N force? J (b) What is the coefficient of kinetic friction between the crate and the surface?

A 4.8 kg box has an acceleration of 1.8 m/s? when it is pulled by a horizontal force across a surface with 4, = 0.50. Find the work done over a distance of 22 cm by the following forces. (Enter your answers in joules.) (a) the horizontal force (b) the frictional force (c) the net work (d) what is the change in kinetic energy of the box?

The graph in the figure below shows the magnitude of the force ex- erted by a given spring as a function of the distance x the spring is stretched. How much work is needed to stretch this spring: (a) a distance of 5.0 cm, starting with it unstretched, and (b) from x - 2.0 cm to x = 7.0 cm? F (N) x (cm) 1 2 3 4 5 6 67 8 350 300 250 200 150 100 50

A tension force of 155 N inclined at 30.0° above the horizontal is used to pull a 35.0 kg shipping crate a distance of 5.10 m on a rough surface. If the crate moves at a constant speed, find (a) the work done by the tension force and (b) the coefficient of kinetic friction between the crate and surface. HINT (a) the work done by the tension force (in J) 688 Forces in the direction of an object's displacement do positive work on the object and tend to increase the object's speed. J (b) the coefficient of kinetic friction between the crate and surface -0 005 Need Help? Read It Watch it

may someone please explain

While doing a chin-up, a man lifts his body 0.40 m. (a) How much work must the man do per kilogram of body mass? (b) The muscles involved in doing a chin-up can generate about 70 J of work per kilogram of muscle mass. If the man can just barely do a 0.40-m chin-up, what percentage of his body's mass do these muscles constitute? (For comparison, the total percentage of muscle in a typical 70-kg man with 14% body fat is about 43%.)

A skier of mass 115 kg travels down a ski trail. Suppose the ski trail is not frictionless. (a) If the top of the trail is a height 180 m above the bottom, find the work done by gravity on the skier. J (b) If the skier has a speed of 36 m/s at the bottom of the hill, what is the work done by friction on the skier? (Assume the skier starts at rest at the top of the hill.) J

A person pulls a toboggan for a distance of 37.8 m along the snow with a rope directed 21.5 ° above the snow. The tension in the rope is 88.2 N. (a) How much work is done on the toboggan by the tension force? (b) How much work is done if the same tension is directed parallel to the snow?