Work and energy Definition and 338 Threads

Homework Statement Two springs which have spring constant of k1 and k2 respectively are vertically hung in a series. Then, a mass m is attached to the end. Find the displacement and the spring constant of this series. Homework EquationsThe Attempt at a Solution I got the displacement x1+x2...

Homework Statement ( The following problem is taken from kleppner's " Introduction to mechanics" ) ( The question in the book talks about the velocity but my confusion is related to the Energy ) Homework Equations Conservation of Mechanical energy : Ef - Ei = 0 Consevation of Momentum : Pf -...

Homework Statement How do we determine a specific force mentioned in a question to be conservative or non-conservative? 2. Relevant data Conservative force is a force whose work done does not depend on the path that is taken while doing it. Examples include electrostatic force, gravitational...

If we have two objects forming an isolated system and their centre of mass is ##X_{com}##, we know by work energy theorem that work done on centre of mass will be ##\int F_{ext}.X_{com}= 0## as no external force is acting on the system. However, if there is internal forces between the objects...

Let's consider a setup consisting of a table with friction, and a block on top of it. Suppose we drag the block across the table with a constant speed. The applied force ##f_{app}## acting through a distance ##d## does a work ##f_{app}d##. The frictional force ##\mu N## is equal to ##f_{app}##...

My book says: "Let us derive an expression for the potential energy associated with an object at a given location above the surface of earth. Consider an external agent lifting an object of mass ##m## from an initial height ##y_{i}##above the ground to a final height ##y_{f}##. We assume the...

Hello, I've submitted 8 topics already but sadly it was all rejected, I could really use some help to look for investigatory projects about physics

A pendulum of mass m and length l is suspended from the ceiling of a trolley which has a constant acceleration a. Find the maximum deflection θ of the pendulum from the vertical. When I used work energy theorem, I got θ = 2 arctan(a/g). But when I took the equilibrium position and equated the...

Homework Statement Two blocks are connected with a massless, non-stretchable rope, and connected to a spring that is fixed to a wall. One of the blocks is hanging from the side of the table, while the other lies on the table. The mass of each block is m=1.0 kg, spring stiffness is k=50 N/m...

Homework Statement A fireman of mass m slides a distance d down a pole. He starts from rest. He moves as fast at the bottom as if he had stepped off a platform a distance h≤d above the ground and descended with negligible air resistance.What average friction force did the fireman exert on the...

I am having hard time understanding the definition of work done to move a charge in an electrostatic field book says that if charge A and B sitting at some position and now if I move the charge say A towards B from arbitrary direction that force required is exactly equal and opposite to the the...

Can someone check if I'm doing this problem correctly? Please tell me if I did anything wrong. 1. Homework Statement A 12 g bullet passes horizontally through a 15 cm tall, 20 cm long .5 kg block which is initially at rest on a 1 meter tall table’s edge. The bullet is initially moving 230 m s...

Homework Statement Hi! I'm having issues with this practice problem. Any advice on what I'm doing wrong would help! A 2.5 kg particle is projected with an initial speed of 3.3m/s along a surface for which the coefficient of friction is 0.7. Find the distance it travels given that the particle...

Homework Statement Rotation of a small drum of mass moment of inertia 0.44kg.m^2 and with frictional resistance torque 0.3 N.m is initiated by a string wound around its 20 mm diameter shaft and attached to a stretched spring, as shown in the figure. If the spring, which has a stiffness 2N/mm is...

K= ∫mvdv = ∫m dx/dt dv = ∫m dx/dv dv/dt dv = ∫m dv/dt dx = ∫Fdx = U => K=U, why isn't this true? If it is, wouldn't that mean that Kinetic Energy is always equal to Potential Energy?

Homework Statement Problem: http://imgur.com/a/Sw2zA Hi all, I was given this problem as homework and I have almost no clue on how to solve it. I have tried for some time with no luck. Homework Equations We learned about kinetic and potential energy as well as work. W = F*d W = delta KE PE =...

Hi guys. I'm new to this forum so I'm not sure if I'm posting this in the right place or correctly, but I was totally stumped on a Physics 12 question as I was studying for my exam. The question is: An explorer spacecraft is descending towards Mars using a rocket engine for braking. The...

1. The dilemma Work (change in energy) is defined as the exertion of a force over a distance parallel to the force. So if force is exerted, but nothing is moved (presumably with two immovable objects), then no energy is changed. But think about the dilemma with a person lifting 100 pounds...

Homework Statement A person exercises daily by lifting weights. When he lifts a weight, he is exerting a force on it to displace it. This means he is doing work and therefore burning calories. But when he lowers the same weight, does he do any work and burn calories? Homework Equations W = F x...

Homework Statement A uniform ring of mass m and radius r is projected horizontally with velocity v on a rough horizontal floor,so that it starts off with a pure sliding motion and it acquires a pure rolling motion after moving a distance d.If the coeffcient of friction between ground and ring...

I am confused of how Work basically equals to Kinetic Energy...I will give an example just as way to help you help me get an idea about how it works...the example I thought of is... '' James (100 kg) jogs on a straight road at a constant velocity of 2.2 m/s for 600 seconds, how much energy does...

Homework Statement In bicycling, each foot pushes on the pedal for half a rotation of the pedal shaft; that foot then rests and the other foot takes over. During each half-cycle, the torque resulting from the force of the active foot is given approximately by τ = τ0 sin ωt, where τ0 is the...

Homework Statement Verify the Work-Energy Theorem W=ΔK for a bead of masd m constrained to lie on a frictionless stick rotating with angular velocity ω in a plane. Homework Equations W =∫ F⋅dr, K =m/2 v^2 [/B] The Attempt at a Solution Adopting polar coordinates the velocity is v = r' +r*Θ'...

Homework Statement A red van came through and crashed into a green van. The driver of the red van claims that he was driving at a speed of 11 meters/second at the moment of the crash. You want to find out if his claim is true. a. the mass of the red van is 1000 kg b. the mass of the green van...

I have been stuck on this physics question: An object is sliding along a flat surface with an initial speed of 30 m/s. What must the coefficient of kinetic friction be between the object and the surface if the object slides to a stop in 10m? What would be the speed of the object after it had...

Homework Statement To measure the combined force of friction (rolling friction plus air drag) on a moving car, an automotive engineering team you are on turns off the engine and allows the car to coast down hills of known steepness. The team collects the following data: (1) On a 2.70° hill, the...

Homework Statement A 125 - G arrow is shot vertically upwards with a Vi of 28/ms. Assuming a 20% loss in Mechanical Energy while ascending, what maximum height above the position it was shot does it reach? Homework Equations Vi= 28m/s Vf= O m/s D= ? a= -9.8 m/s Vf^2= Vi^2 + 2aD Eg = mgh Ek =...

Homework Statement A 26.2 kg child rides a 1.00 kg potato sack down a 2.05 m high slide. If the child starts from rest and has a speed of 1.60 m/s at the bottom of the slide, what is the change in thermal energy of the child on their potato sack and the slide? Homework Equations KE = (1/2)mv2...

Homework Statement A child pulls a trolley by the handle along a flat sidewalk. She exerts a force of 80.0 N at an angle of 30.0° above the horizontal while she moves the wagon 12 m forward. The force of friction on the trolley is 34 N. Homework Equations (a) Calculate the mechanical work done...

Homework Statement Consider two observers moving with respect to each other at a speed v along a straight line. They observer a block of mass m moving a distance x on a rough surface. The following quantity (or quantities) will be same as observed by the two observers: (a) kinetic energy of...

Homework Statement The coefficient of friction between the block of mass m1 = 3.00 kg and the surface shown is µk = 0.400. The system starts from rest. What is the speed of the ball of mass m2 = 5.00 kg when it has fallen a distance h = 1.50 m? Note that this is just a generic picture of...

Homework Statement Stretchable ropes are used to safely arrest the fall of rock climbers. Suppose one end of a rope with unstretched length ##l## is anchored to a cliff and a climber of mass m is attached to the other end. Ehrm the climber is a height ##l## above the anchor point, he slips and...

Homework Statement Question :- A block of mass ##5 kg## is attached to a spring. The spring is stretched by ##10 cm## under the load of the block. A impulse is provided to the block such that it moves up with a velocity of ##2 m/s##. Find the height it will rise. Homework Equations ##F_s =...

Homework Statement Two metal spheres of equal radius ##R## are placed at big distance one from the other. Sphere 1 has total charge ##q## and sphere 2 has no charge. The two speheres are moved one towards the other until they touch, then they are moved again far away one from the other. What is...

Hello. I'm new to physics, and the problem I have seems so basic, mathematically speaking. I'm just failing to grasp exactly what is being asked. If I can find that, I believe I can find the answer. Here it is: 1. Homework Statement Let A = x2ˆx + y2ˆy + z2ˆz Consider the parabolic path y2 =...

Homework Statement I'm looking to the distance (h) a ski jump should be placed from the top of the hill so that a skier with a mass of 85kg will not exceed 30.0m/s. I am given an initial velocity of 2.0m/s and the total work of frictional forces to 4000J Homework Equations How can I use total...

I know that for rigid bodies only the work-energy theorem states that the net work done on the body equals the change in kinetic energy of the body since a rigid body has no internal degrees of freedom and hence no other forms of energy such as potential energy. Is there a most generalized form...

Homework Statement A cord is used to vertically lower an initially stationary block of mass M = 35 kg at a constant downward acceleration of g/5. When the block has fallen a distance d = 6.5 m, find the work done by the cord's force on the block. Find the work done by the weight of the block...

Homework Statement On a train, there is a passenger who has an aquarium, filled with water. The aquarium's size: 40cm x 25cm x 25cm, and is filled with water up to the height of 20cm (5 cm remaining) What is the maximal deceleration of the train, such as the entire volume of water will remain...

Homework Statement A force F acts over the block as show in the figure. F have a constant magnitude, but has a variable direction. The direction of F, at any given instant, always is directed to the point P. Evaluate the work done by the force F through the displacement d between the points R...

Homework Statement Lifting a box (150 kg) up for 20 meters in 10 minutes, how much horsepower needed? Homework Equations 1 Watts = 1 Joule/sec 1 Horsepower = 746 Watts The Attempt at a Solution I've figured this out but I got a very low horsepower :( about 0.065 hp, does it correct?

Homework Statement attempt to derive the equation of centripetal acceleration using work energy theorem Homework Equations work done = Change in kinetic energy The Attempt at a Solution consider diametrically opposed points occurring in uniform circular motion - displacement = 2*R and let...

This (photo) is a very typical example of conservation of angular momentum, but my trouble arrises from trying to prove that the difference of energy will have to correspond to work, by calculating the work done by you to alter the moment of inertia. I have spent a lot of time in this, but I...

Homework Statement Refer to figure. Homework Equations U=Fs T=.5mv^2 Vg=mgh The Attempt at a Solution I am not exactly sure where to start. I would appreciate if someone could nudge me in the right direction and then go from there.

Homework Statement Cylinder A (mass = 5kg) is released from rest at a height h =100mm above a spring of stiffness k = 1.8 kN/m. Determine, (i) the maximum compression of the spring, (ii) the spring deflection when the cylinder’s velocity is a maximum, and, (iii) the maximum velocity of the...

Homework Statement A body moves a distance of 10 meter along a straight line under the action of a force of 5 Newtons. If work done is 25 joules, the angle which the force takes with the direction of motion of the body is: a: 0 degree b: 30 degree c: 60 degree d: 90 degree Homework Equations...

Work unit is said to be Joule and Energy unit is also Joule. Work formulas in F x S ( Force x Displacement) . We know 1 J = 1 F x `1 s Now Energy is also measured in Joule(J) So can we state : E = 1 F x 1 s as 1 J = 1 F x 1 s that is E = W Then why work and energy are different by definition...

Homework Statement 1) According to an object's distance vs. force (parallel) graph, what is the work done in this process as the object moves from 2 m to 8 m? 2) a book is pushed up an 8 degree inclined plane with an initial speed of 11 m/s. If the coefficient of kinetic friction between the...

Homework Statement Hey guys. I have a problem to solve but I am stacked and I don't now how,so any help will be hghly appreciated.The problem is the following: A truck of mass 9000kg is moving with speed 18m/s, when the driver decides to stop and applies the brakes. After 6s the truck stops...

Starting from rest, 1-kg block slides down a frictionless curved ramp, which is one quadrant of a circle, and gains 60 J of kinetic energy at the end of the curved path. The block then slides on a 6-m long rough horizontal surface and acquires a speed of 9 m/s just before going up a rough plane...