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A force is said to do work on an object when the body it acts on has a displacement of the point of application. Force does work when it results in movement. The SI unit of work is a newton-metre or joule (J).

Work was introduced in 1826 by a French mathematician Gaspard-Gustave Coriolis. [1] He described work as the “weight lifted through a height”. This was based on the early steam engines ability to life buckets of water out of flooded mines.

Work done by a constant force of magnitude F on a point that moves a displacement d is:


For moving objects, the quantity of work/time is calculated as a distance/time, or velocity. Thus at any instant, the rate of work done by a force is the scalar product of the force and the velocity vector of the point of application. The small amount of work done over an instant of time is calculated as:


To calculate the work over a distance can be calculated by integration. The derivation leads to:

W=Fd cosθ

Oscillations near the equator.

Consider (unrealistically) a perfectly spherical rotating planet whose g value is constant over the surface. A bead lies on a frictionless wire that lies in the north-south direction across the equator. The wire takes the form of an arc of a circle; all points are the same distance from the center of the earth. The bead is r

Understanding Work, Energy & Power

Explain the concept of Work, Energy and Power. Also describe various types of mechanical energy compared to kinetic energy and potential energy and inter relation between them.

Solving Basic Physics Problems

1) If you do 100 J of work to elevate a bucket of water, what is its gravitational energy relative to its starting position? 2) Suppose two blocks of ice are heading towards each other. Block A has a mass of 4.24 kg and is traveling at 2.24 m/s. Block B has a mass of 4.42 kg and is traveling at 2.24 m/s in the opposite directio

Hydraulic Cylinders

Explain how power is created using hydraulics and how a little cylinder on the tractor can raise or lower extreme amounts of implement weight. Explain the system including parts and functions.

Block of mass 2.5 kg is placed against a compressed spring

Please refer to attachments for details. 6. A block of mass 2.5 kg is placed against a compressed spring (k = 2900 N/m) at the bottom of an inclined plane, as shown. When the spring is released the block is projected up the incline and the spring expands by 14 cm to its normal length. Calculate the maximum distance travele

Physics Kinematics Multiple Choice

Sample Question: To cause a 25 kg object to experience an acceleration of 2 m/s2 the net force that needs to be applied to the object is Please see attached to view the rest of the multiple choice questions.


A 90kg box is pushed by a horizontal force F at constant speed up a ramp inclined at 28 degrees. Determine magnitude of applied force a) when ramp is frictionless b) when coefficient of kinetic friction is .18

Work done by a varying force.

An object is under the force F = (k1*x) i - (k2*y) j. Calculate the work done by this force when the object: a) moves on the x-axis from the origin to the point (a,0), and then goes from (a,0) until (a,b) parallel to the y-axis; b) moves from the origin to the point (0,b), and then goes from (0,b) until (a,b) parallel to t

Force and Flooding Problems

The story goes that a boy in Holland saved his country from being flooded by plugging a hole in the sea wall with his finger. Parts of Holland are lower than sea level and walls have been built to keep the sea out. If the hole was 2.00m below sea level and the density of the North Sea is 1030 kg/m3. a) What was the force on h

Six problems on mechanics.

(Please see the attachment for questions, complete with diagrams/figures) 2. If the 10-kg ball has a velocity of 3 m/s when it is at the position A, along the vertical path, determine the tension in the cord at this position and the magnitude of acceleration of the ball at this position. 3. The 2-Mg car is being towed by

Work, Energy, Velocity & Power: Example Questions

Problem 1: The dumbwaiter D and its load have a combined mass of 300kg, while the counterweight C has a mass of 400 kg. Determine the power delivered by the electric motor M when the dumbwaiter: (a) is moving up at a constant speed of 2.5 m/s; (b) has an instantaneous velocity of 2.5 m/s and an acceleration of 0.75 m/s^2,

Kinetic Energy, Point Charges, Electric Field and Potential

A charged particle with a charge of +5.0 micro coulombs is initially at rest. It is accelerated through a potential difference of 500 V. What is the kinetic energy of this charged particle? Two point charges of magnitude +4.00 MicroC and +2.00 microC are placed at opposite corners (top right, lower left) of a rectangle 0.800m

Work and Energy Problems

Questions: Work and Energy Review Problems (Answers are at the bottom of this document) 1. From the given list, select a possible pair for the value of coefficient of static and kinetic frictions μs and μk (There may be more than one choice) a. (2.61, 2.00) b. (2.00, 2.61) c. (0.261, 0.150)

Using point charges to determine potential at a given point

3 point charges Q1, Q2, Q3 are located in the xy plane at points (-10,0), (10,0) and (-5,12) respectively. The charges are given values Q1 = 5 uC, Q2 = -10 uC, Q3 = 8 uC. You may assume that the distance between charges is in units of cm (A) Calculate the Electric Potential at the origin, point (0,0) (B) Determine the

Work, Energy & Power Physics

The motor of a ski boat generates an average power of 6.90 x 10^4 W when the boat is moving at a constant speed of 15 m/s. When the boat is pulling a skier at the same speed, the engine must generate an average power of 8.70 x10^4 W. What is the tension in the tow rope that is pulling the skier? The drawing shows the force-v

bullet hitting a wooden block

A bullet with a mass of 3.00 g, traveling horizontally with a speed of 420 m/s, is fired into a wooden block with mass of 0.840 kg , initially at rest on a level surface. The bullet passes through the block and emerges with its speed reduced to 180m/s . The block slides a distance of 48.0 cm along the surface from its initial po

Electrostatic potential energy & electrical potential

See attached file. The problems are from Physics 7th edition by Cutnell & Johnson. 1. During a particular thunderstorm, the electric potential difference between a cloud and the ground is Vcloud - Vground = 1.90 108 V, with the cloud being at the higher potential. What is the change in an electron's electric potential ene

Work done by pressure forcing water through a pipe

Problem 61 How much work is done by pressure in forcing 9.6 m3 of water through a pipe having an internal diameter of 13 mm if the difference in pressure at the two ends of the pipe is 3.2 atm? Problem 81 Tin can has a total volume of 1380 cm3 and a mass of 146 g. How many grams of lead shot of density 11.4 g/cm3 could

Seven Physics Problems

Please show work. 1. Consider the energy of a 100 kg rock. a) What is the gravitational potential energy (PE) of the rock that is on a table 5 m above the ground? b) The rock falls to the ground. What is its PE on the ground? c) What is the change in PE of the rock from the table to the ground? d) From conservation of e

Linear momentum, bullet's energy, and billiard ball rebound

For the following problems, the answers are given. Show the workings to arrive at the correct answers. 1. If a 60 kg woman is riding in a car travelling at 90km/h, what is her linear momentum relative to (a) The ground (b) the car? Answer: (a) 1.5 x 10^3 kg.m/s (b) zero 2. A 5-g bullet with a speed of 200m/s is fired ho

Beam Balance: Principle of Lever

1) Let's say you are holding a bag of potatoes that you want to buy. The seller tells you that it will cost $0.34 per lb. He then tells you that it weighs 10.0 pounds. You really want these potatoes; there are no potato sellers within miles and you are tired. You have a problem; you don't trust this guy selling the potat

Questions on Classical Mechanics

1. You are loading a spring loaded dart gun and do an amount of work W such that the spring is only 1/3 compressed. How much additional work must you do to fully compress it from 1/3 to fully compressed? Answer in terms of W. 2. A large man tosses a small child onto a large pile of leaves. During the toss, the man exerts ___

Four questions on mechanics

1. A person standing on the floor is leaning against a wall. The wall exerts on the person a force of 100 N in the horizontal direction. What other horizontal force keeps the person in equilibrium? 2. Torque is measured in Newton meters. Work can also be measured in Newton meters. What are the quantities measured in m

Momentum is explained.

If any conversions are done kg has to be to N or lbs to N and units after answers. 1.) What is linear momemtum of a 198 kg aircraft going 48.3m/s 2.)a 240kg cart runs into the rear of a 134kg cart that is stationary the two carts lock together after the collision and move with a speed of 13.8m/s what is the speed of the

Physics - Quantum Mechanics - Photons

Please help with the following problems. (1) Suppose that a photon has energy of 5 x 10 -19 J. (five times ten to the negative 19th Joule) What's the wavelength of this photon? What is its frequency? (2) The photon in the above problem strikes a metal plate that has a work function of PHI = 3 x 10 ^ -19 J. What's the max

Forces that saved a paratrooper's life

A paratrooper pilot fell 360 m after jumping without his parachute opening. He landed in a snowbank, creating a crater 1.5 m deep, but survived with only minor injuries. Assume the pilot's mass was 80 kg and his terminal velocity was 50 m/s. (a) Estimate the work done by the snow in bringing him to the rest. (in J) (b) Estim

Coefficient of kinetic friction, incline

A child slides down a slide with a 30 degree incline, and at the bottom her speed is precisely half what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child. Police lieutenants, examining the scene of an accident involving two cars, measure the

tensions in the strings and accelerations of the object

Please see the attached file. An object of mass m1 on a frictionless horizontal table is connected to an object of mass m2 through a very light pulley P1 and a light fixed pulley P2 as shown below. (a) If a1 and a2 are the accelerations of m1 and m2, respectively, what is the relation between these accelerations? (

3 good questions in mechanics: Force, work and energy.

Please see the attached file for full problem description. 1.) To immobilize a fractured femur, doctors often utilize the Russell traction system illustrated in the figure below. Notice that one force is applied directly to the knee, F1, while two other forces, F2 and F3, are applied to the foot. The latter two forces combine