Work and energy Definition and 338 Threads

Homework Statement Hello, I am having trouble understanding the logic behind the solution to the posted problem. How did they deduce the equation for "Just after impact" ? I don't see how $$v_y = \sqrt{2g(0.6)}$$ What assumptions did they make or how did they get this simplified equation? I...

Homework Statement A screen grab of a DataStudio run with a cart being pulled by a rubber band connected to a force sensor attached to the end of the track is shown below. The two graphs have the same horizontal axis: position of the cart from the motion sensor. The vertical axis on one graph...

Homework Statement Is the statement cirrect: "the rate at which a wave transfers energy depends on the amplitude at which the particles of the medium are vibrating." And does the energy=A^2 ? Homework Equations E (proportional) A^2 The Attempt at a Solution For the statement I am about...

1. The problem statement, all variables and given/known force F = (4x i + 3y j) acts on object as it moves in the x direction from the origin to x=5m. What is the angle between the force and the displacement Homework Equations I'm not really sure since I have no idea The Attempt at a Solution...

This is something that's bugged me since I've read about it. What does it mean to say "energy is the capacity to do work"? I've read somewhere that work is some sort of integral. But I'm still confused, what do we mean when we say "the energy of object x is so and so"? I know the two quantities...

Homework Statement Tarzan (mass of 80kg) has an 18m vine stretched horizontally from his hut to a pivot point P, as shown. He uses it to swing across the gorge to visit Jane's hut, starting from rest to conserve energy. One day Jane spoiled his plans by fastening a strong, thin, smooth...

Homework Statement A body of mass 8.0 kg is initially at rest on a horizontal frictionless surface. A force of 18 N acts on it and accelerates it to a final velocity of 12 m/s. Calculate (a) the distance travelled, (b) the work done by the force, (c) the final KE of the body...

A cross-country skier ascends a peak and rises 300 m vertically during the ascent. Her mass including clothing skis, poles, shoes and backpack is 65 kg. (a) Find the minimum mechanical work needed to be done by the skier (neglect friction). (b) Why do we not need to consider the skier’s...

Homework Statement i just want everybody to check if my solution is correct.. because I am not confident with this one.. your help would be highly appreciated Question: The 0.31kg mass slides on a frictionless wire that lies in the vertical plane. The ideal spring attached to the mass has a...

Homework Statement At a carnival, you can try to ring a bell by striking a target with a 9.00-kg hammer. In response, a 0.4-kg metal piece is sent upward toward the bell, which is 5.00 m above. Suppose that 25.0% of the hammer’s kinetic energy is used to do the (non- conservative) work of...

Homework Statement A wrecking ball swings at the end of a 10.0-m cable on a vertical circular arc. The crane operator manages to give the ball a speed of 6.00 m/s as the ball passes through the lowest point of its swing and then gives the ball no further assistance. Friction and air resistance...

Homework Statement A sled is being pulled across a horizontal patch of snow. Friction is negligible. The pulling force points in the same direction as the sled's displacement, which is along the +x axis. As a result, the kinetic energy of the sled increases by 38% . By what percentage would the...

Homework Statement You get a new job working for a railroad company and your first task is to work out the refuelling strategy and fuel budget for the new trains. Your company has recently purchased charger locomotives which have a mass of 120,000kg and a top speed of 210km/h and run on diesel...

Homework Statement A person starts to mow a lawn with 50kg old fashioned push lawn mower. The handle of the mower makes an angle of 45 degrees with the sure of the lawn. A 200 N force is applied along the handle of the mower by the person a. Determine the normal force exerted by the ground on...

A vertical spring with spring constant 300 N/m is compressed 0.06 m and a 0.25 kg ball placed on top. The spring is released and the ball flies vertically upward. What is the ball's speed when it has gone 0.1 m high? I don't know which relationship is required to find the speed, Can someone...

Homework Statement Truck brakes can fail if they get too hot. In some mountainous areas, ramps of loose gravel are constructed to stop runaway trucks that have lost their brakes. The combination of a slight upward slope and a large coefficient of rolling friction as the truck tires sink into...

I thought of this recently, and want to know if there's something I'm missing. So, say a very fragile object decelerates to a stop from a given velocity. For example, a free-falling object hitting the ground. But, all the kinetic energy is absorbed through use of some clever mechanics (assume...

Homework Statement 40 kg crate is pushed at a constant velocity along an incline with a vertical height of 4 m and inclined distance of 7 m. How much work was done on the crate in moving it to the top of the ramp? For the incline, think of a right angle triangle with the 7 m being the...

I'm going through a few exercises on Schaum's outline college physics, the section on work and energy. It says "In general, the work done against gravity in lifting an object of mass m through a vertical distance is mgh". So they are basically saying that the work donde to lift an object is...

I understand that: 1) For work to be done there must be a force (or a component of it) exerted upon an object, causing it to move. Work done on a system puts energy into it. 2) If the force is applied in the opposite direction to that of the object’s displacement, then the work done by that...

I apologise for what is probably merely stupidity on my part, but has been vexing me for rather a while, and no one I ask can provide any insight. A body undergoes two accelerations. The first is from 0 to 10 m/s, the second from 10 to 20 m/s. For simplicity's sake I will say F= 1N, a= 1 m/s2...

Homework Statement I've been attempting this problem all day now. My current submissions are 10.6N and I keep getting 7.04N every time I retry it but this is also wrong. Can somebody please help me out so I can figure out what I'm doing wrong? Thanks for any help in advanced! The 3.35kg collar...

Hey everyone, first post in here, I'll try to keep it as appropriate as I can. To put it simply, I'm stumped. The vague setup is a vertical ideal spring attempting to push up a mass against gravity. We have everything we need to get the force, but... I can't calculate the direct transference...

The rest if the question ask me to find the the point at which the ball will have maximum speed ? I don't know how to approach it exactly? From my conceptualization I can see that the maximum will be when the spring returns to the uncompressed position at 5.0cm. However the answers disagree and...

Homework Statement As the water in a river approaches a 10.0m vertical drop, its average speed is x m/s. As that water falls, its kinetic energy increases. The speed of the water based on 1kg of mass is 14.9m/s just before it hits the ground. Find the average speed of the river water before...

How can we define negative work to be? I can't get my head around negative work or energy. However, I'm thinking that it must be work that is done opposite in the direction of motion of a particle or body (say, friction). Could someone please help me understand this concept?

If I say 'a system has 5 Joule energy' then will it be equivalent of saying 'a system can do 5 Joule of work' ? And also will it be equivalent to say 'a system can give 5 watt of power for 1 second' ? If so, then which is the basic property of a system? Work, Power or Energy?

Homework Statement A block of mass m is suspended through a spring of spring constant k[I/] and is in equilibrium. A sharp blow gives the block an initial downward velocity v. How far below the equilibrum position does the block come to an instantaneous rest? Homework Equations...

Homework Statement Doug pushes a 5.30 kg crate up a 2.20-m-high 20 degrees frictionless slope by pushing it with a constant horizontal force of 27.0 N. What is the speed of the crate as it reaches the top of the slope? a) Solve this problem using work and energy. Homework Equations...

Homework Statement A box of mass M is at rest on a horizontal table. The coefficient of static friction between the box and the table is k. The box is connected by a taut string to a block of unknown mass m, initially held horizontally as shown and then released. The box begins to slide at the...

Homework Statement a 73kg skier coasts up a hill inclined at 9.3 degrees to the horizontal. friction is negligible. Use the work and energy theorem to determine how far along the hill the skier slides before stopping, if the initial speed at the bottom is 4.2m/s Homework Equations w=Ek...

Homework Statement a 73kg skier coasts up a hill inclined at 9.3 degrees to the horizontal. friction is negligible. Use the work and energy theorem to determine how far along the hill the skier slides before stopping, if the initial speed at the bottom is 4.2m/s Homework Equations w=ek...

NOTE: I know this seems like quite a bit, but it's really not! Most of the questions involve simple 1-line equations, so please don't be discouraged by the amount of text - any assistance is greatly appreciated :) Homework Statement A 6kg steel ball moving at 4m/s hits a 6kg putty ball...

Ignorant as it sounds, what 1kW of energy spent on having moved an object from point A to point B would be really spent on ? Is it, 1. acceleration /desceleration of all moving parts of both the engine and the object itself, and 2. overcoming by all moving parts (including electrons in wires) of...

You've taken a summer job at a water park. In one stunt, a water skier is going to glide up the 2.0m high frictionless ramp, then sail over a 5.0m wide shark tank. You will be driving the boat that pulls her to the ramp. She'll drop the tow rope at the base of the ramp as you veer away. What...

Homework Statement If the cord is subjected to a constant force of F= 300 and the 16kg smooth collar starts from rest at A, determine the velocity of the collar when it reaches point B. Neglect the size of the pulley. Homework Equations (\frac{1}{2}mv12) + \sumU1-2 =...

Is power a quantity defined by: \frac{dU}{dt} and \frac{dW}{dt} Is it just defined to be it, or can it be derived in terms of the other (I mean, dU/dt in terms of dW/dt and vice versa)? I now there's physical motivation to it, but sometimes I just can't help trying to ponder how these equations...

Homework Statement I have to solve this question in two ways, the first is from kinetics and kinematics and the second from the principle of work and energy. For the the first problem I obtained 3.160643122 for the acceleration at b(pulley with force t) and proceeded to find to find the...

A block of mass 10kg is pulled along a straight horizontal road by a constant horizontal force of magnitude 70N in the direction of the road. The block moves in a straight line passing through two points A and B on the road, where AB = 50m. The block is modeled as a particle and the road is...

Homework Statement part a and b are solved(is it correct), but I am not sure how to solve part c. A single constant force F = (3.02i + 5.45j)N acts on a 3.69kg particle. a) Calculate the work done by this force if the particle moves from the origin to the point having the vector...

An object with inertia m = 1.5 kg is connected to a spring with spring constant k = 250 N/m and equilibrium position at x0 = 5 cm (for x > x0, the force is directed toward the origin). The object is initially at rest at position x = 10 cm. You grab the object and move it slowly to position x =...

I have attempted each problem, but am getting lost on just what to do to solve. If i could be pointed in the right direction on how i should go about each problem that would be nice. Attached are my attempts at problems 1-3. Homework Statement SEE ATTACHMENT The Attempt at a Solution See...

One question about this excercise. Why "W" isn't included in the sum of forces? Is doing work because is in the same direction of the movement, so I would assume that both the force of spring and weight would be in in my sum of forces. But this is not the case here, why is that?

For some reason I am getting stuck with problems that seem to be very simple. I get quite confused with the matter that, when fields do negative work, an object gains energy. So, for example. When we raise a book to a shelf, we are doing positive work equal to mgh and gravity is doing...

Homework Statement See attachment "problem" Homework Equations Euler's laws of motion (moment equations), work and energy equations The Attempt at a Solution See attachment "work" I did the work for (1) and (2). I end up with two equations: the first is the tension T, the second...

Homework Statement The spring in the figure has a spring constant of 1000 N/m. It is compressed 13.0 cm, then launches a 200 g block. The horizontal surface is frictionless, but the block's coefficient of kinetic friction on the incline is 0.220. What distance does the block sail through the...

Homework Statement The chain of a workshop crane is 50 m long and has a mass of 3 kg/m. It is partially wound on a drum and the effective radius from the axis of the drum to the chain centre line is 0.2 m. The drum itself, including shaft and gear wheel has a mass of 100 kg and has a radius of...

Homework Statement A wagon having a total mass (including its wheels) of 1000 kg, has four wheels each of mass 100 kg and each having a radius of 0.5 m and a radius of gyration of 0.45 m. The wagon starts from rest at the top of an incline of 1 in 10 (sine). If there is a resistance to...

Griffith's Problem 2.40 (a) and (b) Suppose the plates of a parallel-plate capacitor move closer together by an infinitesimal distance ε, as a result of their mutual attraction. a) Use P= \frac{\epsilon_0}{2}E^2 to express the amount of work done by the electrostatic forces, in terms of...

Taken from An introduction to mechanics - Kleppner, Kolenkow. Problem 4.17 Homework Statement A snowmobile climbs a hill at 15 mi/hr. The hill has a grade of 1 ft rise for every 40 ft. The resistive force due to the snow is 5 percent of the vehicle's weight. How fast will the snowmobile...