Work and energy Definition and 332 Threads

Homework Statement: A perfect hemisphere of frictionless ice has radius R=6.5 meters. Sitting on the top of the ice, motionless, is a box of mass m=6 kg. The box starts to slide to the right, down the sloping surface of the ice. After it has moved by an angle 20 degrees from the top, how much...

Homework Statement: Mike the Mailman takes his oath seriously: "Neither snow, nor rain, nor heat, nor gloom of night stays these courageous couriers from the swift completion of their appointed rounds". Even though a blizzard is raging outside, he goes out to deliver the mail. He makes four...

E final = (1/2)(500)(1.14012)^2 = 324.968 J E initial = (1/2)(500)(0.5)^2 = 62.5 J E final - E initial = 262.468 J

I have tried using Conservation of Energy but I'm getting incorrect answer.

Hey everyone I'm struggling on the last part of this assignment. I need to find the total work done by the block and the bullet, when the collision happens. The informations is: mblock=0.3 kg mbullet=0.01 kg vg=700 m/s Height=0.72m The final speed after the collision is vf=22.6 m/s and the...

Based on my understanding, Top Tank Refilling Advantage: Atmospheric Pressure Disadvantage: High Head (Requires more distance, thus more Work since W = f x d) Bottom Tank Refilling Advantage: Low Head Disadvantage: High Static Pressure (Requires more Force, thus more Work since W = f x d)...

My attempt at the solution... I only have problem in solving part a) 1) i calculated the spring force actingbon the table block and it is greater than the frictionnand tension force acting in the opposite direction, so by that the block will move in left. 2) now i found that which forces are...

$$W = - \int _ { a } ^ { b } \vec { F } \cdot d \vec { r }$$ ( The Force here is referring to the applied force, When moving a positive charge towards another positive charge(stationary) / field In this formula why there is a negative sign in the formula? I am not asking the sign of the total...

iam not sure of the direction of work , is it positive becouse pulleys change the direction of the force ? or is it negative because of the arrow that indicates the direction of acceleration ??!

I was just doing some review on my physics lecture and I stumble on the idea of what if there was an object hanging and the cord mass is also included in the weight and it's displaced upward without having velocity nor time hypothetically and the cord change mass. I tried solving it by W = fΔx...

To find vx vx = dx/t = 3.86 m/1.5 s= 2.573 m/s To find Ek Ek = ½mvx²= ½(79.4)(2.573)²= 262.8 J W = FnetΔd Fnet = 262.8 J/ 3.86 m = 68 N He hits him with a force of 68N

Homework Statement A block is suspended by an ideal spring of the force constant K. If the block is pulled down by applying a constant force F and if maximum displacement of the block from its initial position of rest is X then, find the value of X. Homework Equations mg + F = XK + K(mg/K)...

Homework Statement A cart of mass M1 = 6 kg is attached to a block of mass M2 = 3 kg by a string that passes over a frictionless pulley. The system is initially at rest and the table is frictionless. After the block has fallen a distance h = 1 m: What is the work Ws done on the cart by the...

Homework Statement What is the energy equation for a roller coaster already in motion from the ground with to the top of a full circular loop = point B in the image. My question is would the car still have kinetic energy at the top of the loop? Homework Equations Kinetic Energy Equation...

Homework Statement When bullets are shot on Superman, they bounce off of his chest. 100 Bullets will be shot on his chest per minute, each with a mass of 9g and v= 1000m/s. Assume that the bullets will bounce off elastically back in x-direction. a) What is the average power of all of the...

Homework Statement You are driving with your car (of total mass: 1.2tonnes) with a speed of v=50km/h, until you see an obstacle. a) What is the kinetic energy of the car? b) When you start to brake, there is still 15m until the obstacle. What must be the size of the friction coefficient (µ)...

Homework Statement A 200 kg object moves at 10 m/s at 20m (vertically). It falls to a height of 5 m. Find the new speed. Homework Equations vf²=vi²+2ad The Attempt at a Solution vf²=(10m/s)²+2(9.8m/s²)(15m) vf=19.8m/s To find the distance for the new speed I did 20-5, but I'm not sure it's...

Homework Statement A .5 kg loaded toy (spring k=8000 n/m) loaded toy is compressed .05 m and fired on a flat surface a) Find the new speed it was released with b) If it approaches a hill find the maximum height it can climbHomework Equations KE=1/2kx² KE=1/2mv² PE=1/2kx^2 The Attempt at a...

Homework Statement We shot a projectile with mass ##m## and velocity ##v_0## with angle ##\phi## it collide with a box with mass ##M## at the maximum height of its path. Then, they both start to move with another speed. (We define ##t=0## at this time) (Completely Inelastic Collision). The box...

Homework Statement Question from Fundamentals of Physics (Halliday, Resnick, Walker) This figure below shows a cord attached to a cart that can slide along a frictionless horizontal rail aligned along an x axis. The left end of the cord is pulled over a pulley, of negligible mass and friction...

Homework Statement An object with mass 100 kg moved in outer space. When it was at location < 9,-24,-4 > its speed was 3.5 m/s. A single constant force < 250,400,-170 > N acted on the object while the object moved from location < 9,-24,-4 > m to location < 15,-17,-8 > m. Then a different single...

Homework Statement If we lift a block with constant velocity, by applying a force mg upwards, is the work done zero?Homework EquationsThe Attempt at a Solution The work done must be zero as the resultant force is zero, what I don't understand is how does the block get potential energy if no...

I know that I'm rushing too much but I wanted to see if I can calculate the work of a pendulum that does oscillation with a similar way you calculate the work of a spring. Consider the following free body diagram: Things i noticed: 1) The position is changing both in x and y-axis while the...

Homework Statement A spring has been attached to an object which is kept on the ground. The spring is initially in its natural length: 'l' when a force 'F' is applied on it. The force 'F' slowly pulls the object so it does not attain any acceleration. There's a point 'P' on the line which is...

Homework Statement See question number 5. Homework Equations F=m*a W=F*s Uniform acceleration motion equations The Attempt at a Solution Actually,I am having some difficult understanding the problem. See the F.B.D of the system, see the friction is acting on the block in the forward...

If I lift a 1kg broom stick 1m when holding it from its center of mass, I will have done 9.8J of work and the broomstick would have gained 9.8J of potential energy. If I were instead to lift it from one end I would have to exert a much larger force due to torque. Lifting this same 1kg broomstick...

Homework Statement See question number 3 Homework Equations Work Done="integral" F*ds The Attempt at a Solution I tried to solve this question using integration, I have replaced F with "1" and ds with "t^2+2t". So I am stuck in at that step. Please help me differentiate it further or solve...

Homework Statement Whats is the final speed of the second box(mass = 1kg) when the first one (mass = 5 kg) has descended a distance equal to 0.6 meters in the rough ramp inclined 60° respect the x axis. Consider the spring is compressed a length x = 0.2 meters. The second box is tied to the...

The question is stated as the following: When a 3.60 kg object is placed on top of a vertical spring, the spring compresses a distance of 2.83 cm. What is the force constant of the spring? The correct answer was acquired by using the equation F = mg = -kx, where k is the spring constant and x...

1. The Problem Stament, all variables and given data a 15 kg crate, initially at rest, slides down a ramp 2.0 m long and inclined at an angle of 20 degrees with the horizontal. if there is a constant force of kinetic friction of 25 N between the crate and ramp, what kinetic energy would the...

Information Given:Zero, a hypothetical planet, has a mass of 4.2 x 1023 kg, a radius of 2.8 x 106 m, and no atmosphere. A 10 kg space probe is to be launched vertically from its surface. Question: (a) If the probe is launched with an initial kinetic energy of 5.0 x 107 J, what will be its...

Homework Statement Hi I'm attempting to derive the gravitational potential energy of a point mass (##m##) that's moving from infinity to a point r' inside a gravitational field produced by a another mass ##M##. For simplicity I treated it as a one dimensional case. The problem I get is that the...

Homework Statement A completely filled cylindrical tank of height H contains water of mass M. At a height h above the top of the tank there is another wide container. The entire water from the tank is to be transferred into the container in time T such that level of water in tank decreases at a...

Homework Statement I have to explain the equation W=VIt and apply it to a circuit. But I do not undertsand what the equation shows. Homework Equations W=VIt The Attempt at a Solution My rough guess is : work done is equal to the time (t) taken for 1A of current to flow at 1V

Trying to remember some basics. I know the thrust of a jet engine. I'm thinking about equivalent HP. I can establish HP at a given speed, but what about while accelerating? I will display my ignorance here :( Power for static, non accelerating flight: Power = [Thrust x Airspeed] Thrust...

I have a simulation I'm trying out (for fun). A self-gravitating ball of gas, in deep space. (The sim uses a fixed-time-step for each iteration.) I'd like to use Boyles Ideal gas law, the force of gravity, and energy as internal heat. (I don't want to touch enthalpy unless I don't realize...

The formula Work done = dot product of Force and displacement. However this assumes a constant force F on a particle. What then is work done by a variable force. Watch this video to understand how integral calculus can help us find the work done when the force acting in a particle is variable.

Homework Statement There are three problems: 1. How much power is required to lift a 10.00 kg barbell at a speed of 3.0 m/s? 2.What is the average power supplied by a 70.0 kg firefighter climbing up a ladder in 10.0 s? 3. A man pulls a wagon with a force directed 22.0˚ above the horizontal...

Homework Statement A student pushes a 0.65kg box Ali g a desk. When he stops pushing the book, it moves 85cm before stoping (slowing down in this period). Coefficient of friction between book and Table is 0.27.Calculate the work done on the book by the friction. Should it be positive or...

Homework Statement A 20.0 kg block on a horizontal surface is attached to a horizontal spring of k = 2.0 kN/m. The block is pulled to the right so that the spring is extended 10.0 cm beyond its unstretched length, and the block is then released from rest. The frictional force between the...

I have a question about work. If Newtons 3rd law of motion states there is an equal and opposite reaction for any force. Now if for example I apply 500 Newtons of force on my dresser and move it 5 meters I used 2500 joules of energy. Now because the dresser is equally putting that much force...

Homework Statement 14.11 A boy slides down a water chute, starting from rest a A. Neglecting friction determine his speed (a) at the end B of the chute; and (b) on entering the water at C. Homework EquationsThe Attempt at a Solution for (a): for (b): Do I have to treat the boy at B as...

Homework Statement For a positively-charged particle at the origin, and a negatively-charged particle lying to its right on the positive x-axis, the electrostatic force on the negative charge is attractive, and Coulomb's Law gives the magnitude of that force: F = k |Q1| |Q2| / x^2 k is...

Homework Statement Derive the expression for the work done by the ideal spring on the slider when the slider moves from A to B. Assume that the free length of the spring is (a) ##L_0 = b##; and (b) ##L_0 = 0.75b## Homework EquationsThe Attempt at a Solution Can you check if my solution...

Homework Statement g = ##10m/s^2## ##\sqrt{3}## = 1.7 Determine work by the 20N force Homework Equations for an inclined plane: W = ((F+mgsin30)-(mgcos30)μ)s -> (Fx-ff)*s for object pulled with angle: W= (Fcos60-(mg-Fsin60)μ)s -> (Fx-ff)*sThe Attempt at a Solution W=...

I am confused how a charge could have negative work done. To clarify, I was doing a problem earlier in which a positive charge and negative charge are moving towards each other. I used the equation work = Δv * q And when I was doing this, the change in electric potential, Δv, was negative, and...

Here is problem I quickly made up: Suppose there is a ramp with a height of 6 meters and length of 12 meters. A block of 5 kg is pushed up to the top of the ramp with a constant velocity. The force of friction is 15 N. Here's the confusion: By using the non-conservative force work energy...

Homework Statement In the question, a person is pulling a 156 kg sled up a hill. A 620 N force is used to pull the sled up the hill that has an angle of 29° with the horizontal. The sled is pulled a distance of 26 m, and the kinetic friction coefficient is 0.0622. The system has been defined as...

Good Afternoon Is it correct to calculate the force of a point charge by relating the force to the kinetic energy and this with its derivative? I have the graphic V/r (Velocity Vs Space), want to calculate force, relate work with force in this way: W=ΔEk, in my case the kinetic energy initial is...

Hello, I am confused about the work energy theorem. If someone goes up the stairs at a constant velocity, is work being done on the person? After all, Wnet = change in kinetic energy, and that change is zero. This is the original problem that I am trying to solve, from David Morin's Problems...