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# Work

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### Wooden Crate Motion: Force, Friction, Work done

1) Sally expends 10460 J of energy to drag a wooden crate 24.7 m across a floor with a constant speed. The rope makes an angle of 48.0Â° with the horizontal. (a) How much force does the rope exert on the crate? _____ N (b) What is the force of friction acting on the crate to impede its motion? Magnitude _________ N

### Physics: mover's dolly transports a refrigerator up a ramp

A mover's dolly is used to transport a refrigerator up a ramp into a house. The refrigerator has a mass of 108 kg. The ramp is 2.10 m long and rises 0.850 m. The mover pulls the dolly with a force of 508 N up the ramp. The dolly and ramp constitute a machine. (a) What work does the mover do? ________ J (b) What is the work

### Mechanics: Collision, Friction, Work, Energy

See attached diagram. A movie stuntman (mass = 80.0 kg) stands on a window ledge 5.0 m above the floor (see figure below.) Grabbing a rope attached to a chandelier, he swings down to grapple with the movie's villain (mass = 70.0 kg) who is standing directly under the chandelier. (Assume that the stuntman's center of mass mov

### Work and Energy: Motion on a Skateboard

See attached diagram. Your cousin Throckmorton skateboards down a curved playground ram. Treating Throcky and his skateboard as a particle, his center of mass moves through a quarter-circle with a radius R = 3.0 m (see figure below.) The total mass of Throcky and his skateboard is 25.0 kg. He starts from rest and there is

### 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

### Work & Energy of a hanging rope

A rope having a total mass of 0.4kg and total length 4m has 0.6m of the rope hanging vertically down off a work bench. How much work must be done to place all the rope on the bench?

### 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 ___

### Physics for Bicyclists in Tour de France

Bicyclists in the Tour de France do enormous amounts of work during a race. For example, the average power per kilogram generated by Lance Armstrong (m= 75.0 kg) is 6.50 W per kilogram of his body mass. A) How much work does he do during a 135-km race in which his average body speed is 12.0m/s B) Often the work done is e

### Determining Amount of Work in Joules: Outer Space Example

(a) Determine the amount of work (in joules) that must be done on a 101 kg payload to elevate it to a height of 1005 km above the Earth's surface. _____ MJ (b) Determine the amount of additional work that is required to put the payload into circular orbit at this elevation. _____ J

### A gravitational force case is illustrated.

A pendulum swings left to right. At what locations in the pendulum's swing is the gravitational force doing positive work? Negative work? No work? What is happening to the speed of the pendulum in each case? Where does the pendulum have the greatest gravitational potential energy? Where does it have the greatest kinetic ener

### 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 - Simple Machines (Levers)

Levers, pulleys, and wedges are simple machines. Does the concept of work explain why we use these machines in our daily lives, how they work, and why they work? Explain your reasons in two paragraphs, taking examples from daily life.

### 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

### Physics - Work-Energy Theorem.

A .010-kg bullet traveling horizontally at 400.0 m/s strikes a 4.0-kg block of wood sitting at the edge of a table. The bullet is lodged into the wood. If the table height is 1.2 m, how far from the table does the block hit the floor?

### Physics - Work-Energy Theorem..

A 700kg glider is flying in straight and level flight at 90 m/s. What is the initial kinetic energy of the glider and if the pilot decides to trade airspeed for altitude how much alitude can the pilot gain while slowing the glider to 25 m/s? (Neglect loss of energy due to air friction)

### Force, work & energy

1) The motor of a ski boat generates an average power of 35900 W when the boat is moving at a constant speed of 17.7 m/s. When the boat is pulling a skier at the same speed, the engine must generate an average power of 80700 W. What is the tension in the tow rope that is pulling the skier? 2) The drawing shows the force-versu

### Rotational Speed of a Uniform Disk

A uniform disk with a mass of 895 g and radius 17.0 cm is rotating on frictionless bearings with a rotational speed of 18.0 Hz when Jill drops a 120 g clod of clay on a point 7.90 cm from the center of the disk, where it sticks. What is the new rotational speed of the disk? I was given the equation w=2(pi)F?

### a child slides down a hill

A hill has a height h. A child on a sled (total mass m) slides down starting from rest at the top. Does the velocity at the bottom depend on the angle of the hill if: a) It is icy and there is no friction? b) There is friction (deep snow)?

### 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

### Calculate the force exerted by the man

A 255 kg piano slides 4.4 m down a 30Â° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. a. Calculate the force exerted by the man. b. Calculate the work done by the man on the piano. c. Calculate the work done by the

### Dispersive Waves: Group and Phase Velocity Example Problem

Please see the attached file. In some media, waves of different frequencies travel at different speeds. Such a medium is called a dispersive medium because waves that are not sinusoidal will change shape or disperse over time. For example, a superposition of two such waves of different frequencies is described by the e

### the work done in taking a particale around the circle

Please see the attached file. 4. Compute the work done in taking a particle around the circle x^2 + y^2 = a^2, z = 0 if the force is (a) F = yi, and (b) F = xi What do you conclude about these forces?

### Motion of Particle

A particle of mass m moves under a force F = -c(x^3), where c is a positive constant. Find the potential energy function. If the particle starts from rest at x = -a, what is its velocity when it reaches x = 0? Where in the subsequent motion does it instantaneously come to rest? Answer:V=1/4(cx^4); [Sqrt. (c/2m)](a^2); x = +-a

### Laws of motion and force on cords

Three blocks are connected on the table as shown below. The table is rough and has a coefficient of kinetic friction of 0.500. The objects have masses of 4.00 kg, 1.00 kg and 2.00 kg, as shown, and the pulleys are frictionless. Determine the acceleration of each object and their directions in terms of up, down, left and, ri

### 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? (

### Laws of Motion and Force: Application of Newton's Law

Please see the attached file for full description and diagram. Two objects are connected by a light string that passes over a friction-less pulley. The incline is friction-less, m1 = 2.00 kg, m2 = 6.00 kg, and theta = 55.0 degrees. Answer the following and show all work. Find: a) the acceleration of the objects b) the te

### Balancing forces equilibrium

An iron bolt of mass 50.0 g hangs from a string 38.0 cm long. The top end of the string is fixed. Without touching it, a magnet attracts the bolt so that it remains stationary, displaced horizontally 26.0 cm to the right from the previously vertical line of the string. (a) Find the tension in the string. (b) Find the magne