Physics Work,Power & Energy Level: High School
A 60-lb (267 N) girl slides all the way down a 20 feet (6.1-m) slide that makes an angle of 20 degrees with the horizontal . The coefficient of kinetic friction is 0.10 . Find the work done by the force of gravity . Find the work done by the force of friction . If she starts at the top with a speed of 1.5 ft/s , (0.457 m/s) , what is her speed at the bottom ?
Physics Work,Power & Energy Level: High School
A comet of mass 8.38 x 10^15 kg strikes the earth at a relative speed of 30 km/s . Find the kinetic energy of the comet . Express your answer in "megatons of TNT" . One megatons of TNT releases 4.2 x 10^15 J of energy . The diameter of the crater caused by such an impact is proportional to the 1/3 power of the explosive energy , with a one-megaton explosion causing a crater of about 1 km diameter . Find the size of the crater produced by the comet impact .
Physics Work,Power & Energy Level: High School
Every second , 1200 m^3 of water passes over a 100-m high waterfall . If 3/4 of the kinetic energy created by the falling water can be converted to electrical energy , what is the power output of the generating station ?
Physics Work,Power & Energy Level: High School
A 30-g bullet , initially traveling at 500 m/s , penetrates 12 cm into a wooden block which is rigidly attached to a wall . How much work is done by the block as it stops the bullet ? Find the value of the average force exerted on the bullet by the block ?
Physics Work,Power & Energy Level: High School
A 250 N bag of cement is placed on a 4 meter long plank 1.8 meters from the end . The plank itself weighs 80 N . The two men pick up the plank, one at each end . How much weigh must each support ?
Physics Work,Power & Energy Level: High School
A uniform plank 5 meters long that weighs 300 N rests on two sawhorses 1 meters from each end. How near either end of the plank can a 700 N painter stand without tipping the plank ?
Physics Work,Power & Energy Level: High School
A weightless ladder 6 meters long rests against a frictionless wall at an angle of 60 degrees above the horizontal . A 75 kg person is 1.2 meters from the top of the ladder . What horizontal force is needed at the bottom of the ladder is needed to keep it from sliding .
Physics Work,Power & Energy Level: High School
A horse pulls a cart with a force of 185 N at an angle of 27.0 degree with the horizontal and moves along at a constant speed of 2.50 m/s .a) How much work does the force exerted by the horse on the cart do in 12.0 minutes ?
b) Find the power output of the horse in horsepower .
Physics Work,Power & Energy Level: High School
The work done by a force acting on a particle is shown by the graph in "click here" The curve is given analytically by F = (9N/m^2)x^2 Determine the work done by the force in moving the particle from x = 1 m to x = 3.75 m.
Physics Work,Power & Energy Level: High School
In a collision between two cars , which would you expect to be more dangerous to the occupants : if the cars collide and remain together , or if the two cars rebound backward from each other elastically ?
Physics Work,Power & Energy Level: High School
A box slides across the frictionless surface of the frozen lake . What happens to the speed of the box as water collects in it from a rain shower ?Physics Work,Power & Energy Level: High School
In common speech , we often use the word 'energy' and 'power' interchangeably as if they were synonyms . However in physics the have distinctly different definitions and are not synonymous . Explain the difference between these terms as they are used in physics .
Physics Work,Power & Energy Level: High School
If you push vigorously against a brick wall , how much work do you do on the wall ? Explain .
Physics Work,Power & Energy Level: High School
A simple pendulum 2.0 in length is released from rest when the support string is at an angle of 25 degrees from the vertical . what is the speed of the suspended mass at the bottom of the swing if air resistance is ignored ?
Physics Work,Power & Energy Level: High School
Suppose that a person with a mass of 80.0 kg while running at constant speed , runs up a stairway in 2.0 seconds . If the stairway is 10.0 meters long (measured along the slope) and slopes upward at 30.0 degrees relative to the horizontal , what is the average power generated by the person in ascending the stairs ? Express this power in horsepower . (1hp= 746 watts)