A large roller in the form of a uniform cylinder is pulled by a tractor to compact earth; it has a 180-cm diameter and weighs 10 kN. If frictional losses can be ignored, what average horsepower must the tractor provide to accelerate it from rest to a speed of           14.4 kph in a horizontal distance of 3 m?

A 7.80-g bullet moving at 470 m/s penetrates a tree trunk to a depth of 5.60 cm.(a) Use work and energy considerations to find the average frictional force that stops the bullet.N (b) Assuming the friction force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving.s

A leaky 10-kg bucket is lifted from the ground to a height of 15 m at a constant speed with a rope that weighs 0.5 kg/m. Initially the bucket contains 45 kg of water, but the water leaks at a constant rate and finishes draining just as the bucket reaches the 15-m level. Find the work done. (Use 9.8 m/s2 for g.)

Assume that the energy content in food can be converted to mechanical energy with 100% efficiency. How many chocolate candy bars (each with 330 kcal) would it take to climb Mount Everest (8850 m)? Assume that the mass of the climber, including equipment, is 127 kg. Round up to the nearest whole number.

Thanks to recent satellite data, we know that the North American continent is drifting westward at a speed of about 1cm/yr. We can assume that the solid part of a continent is about 50 kilometers thick. Estimate the kinetic energy that the continental US has as a result of this motion.

A book of mass 6.3 kg is sliding along a level table with an initial speed of 3.8 m/s. The coefficient of kinetic friction between the book and the table is 0.72. The block eventually comes to rest. During this process 30% of the thermal energy generated goes into the book. Calculate the change in thermal energy of the table.

A 39.0 kg box initially at rest is pushed 5.15 m along a rough, horizontal floor with a constant applied horizontal force of 140 N. If the coefficient of friction between box and floor is 0.300, find the following. (a) the work done by the applied force The correct answer is not zero. J (b) the increase in internal energy in the box-floor system due to friction The correct answer is not zero. J (c) the work done by the normal force (d) the work done by the gravitational force (e) the change in kinetic energy of the box The correct answer is not zero. J (f) the final speed of the box The correct answer is not zero. m/s

A 7.80-g bullet moving at 600 m/s penetrates a tree trunk to a depth of 4.50 cm. (a) Use work and energy considerations to find the average frictional force that stops the bullet. ____________________ N(b) Assuming the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving._____________________ s