Work & Energy

Work and Energy

Work & Energy Principles

Articles
Title
A marksman fires a 7.5-g bullet from a 1.2-kg handgun. The bullet strikes a target and generates 500 J of thermal energy as it stops. If the length of the gun barrel is 125 mm, then how much force did the handgun exert on the bullet?
Two cannons fire identical cannonballs with the same amount of powder. The barrel of Cannon 2 is twice as long as the barrel of Cannon 1. How does the velocity of a cannonball fired from Cannon 2 compare with that of the ball fired from Cannon 1?
A 2700-kg cannon fires an 11-kg cannonball. The length of the cannons barrel is 2.44 m. If the powder produces 2.25 X 10^4 N of force, what is the velocity of the cannonball as it leaves the barrel?
A constant net force of 500 N moves a 1000-kg car 100 m. If the car was initially at rest, then what is the cars final velocity?
A 750-kg glider is flying level at 100.0 m/s. A tailwind blows constantly for 1200 m, and the gliders speed increases to 120 m/s. What is the approximate force of the tailwind?
A man pushes a lawn mower with a handle at an angle of 60° to the horizontal. He applies a constant 20-N force along the axis of the handle and moves the lawn mower a horizontal distance of 100 m in 5 min. What is the mans power output?
A car and a pickup truck are moving down the highway. The truck is twice as massive as the car, but it is only moving at half the speed. How does the kinetic energy of the truck compare with that of the car?
A boy pulls a 10-kg box across an ice rink for a distance of 50 m. He exerts a constant force of 10 N on a rope attached to the box at an angle of 60°. How much work has he done on the box?
A man pushes a 100-kg box with a horizontal force of 100 N across a floor for a distance of 60 m in 2 min. What is his power?
A rifle fires a 4.0-g bullet at a velocity of 950 m/s. If the length of the rifle barrel is 1.01 m, then what force does the rifle exert on the bullet?

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