work and energy Definition and Topics - 103 Discussions
In physics, work is the energy transferred to or from an object via the application of force along a displacement. In its simplest form, it is often represented as the product of force and displacement. A force is said to do positive work if (when applied) it has a component in the direction of the displacement of the point of application. A force does negative work if it has a component opposite to the direction of the displacement at the point of application of the force.
For example, when a ball is held above the ground and then dropped, the work done by the gravitational force on the ball as it falls is equal to the weight of the ball (a force) multiplied by the distance to the ground (a displacement). When the force F is constant and the angle between the force and the displacement s is θ, then the work done is given by:
W
=
F
s
cos
θ
{\displaystyle W=Fs\cos {\theta }}
Work is a scalar quantity, so it has only magnitude and no direction. Work transfers energy from one place to another, or one form to another. The SI unit of work is the joule (J), the same unit as for energy.
Suppose I am sliding a block very slowly on a rough surface. If the block has travelled ##d## distance then work done by me is ##W_1=\mu mg d## and that by friction is ##W_2=-\mu mg d##.
Now the energy transferred from me to block is ##\mu mgd## and that taken by friction from block is ##\mu...
This is the solution from my textbook, and I have some questions about the method
The mass of hanging chain : $$m_h =\frac m 5$$
the center of mass of the hanging chain : $$h_1 = - \frac{1} {2} \cdot \frac L 5 = - \frac L {10}$$
(the minus sign here means that it is under the table surface)...
Guys, I have a problem that really needs you guys to help, I know it is a stupid question but please bear with me:
Context:
You have a block on a slope(has friction) you use a string to pull the block up with constant speed.
Problem:
So according to the network theorem, the work net is equal...
As stated, part (a) says that the work done by the gravitational force ##\vec{F_g}## is 59 kJ. If ##W_T## is the work done by the elevator cable during the 12 m fall, then using the work-kinetic energy theorem,
\begin{align*}
K_f -K_i &= W_g + W_T\\
\frac12m({v_f}^2 - {v_i}^2) &= 59000 + W_T\\...
i can't manage to grasp the concept of PV work in thermodynamics, for example we all know that W= integral(F*dx) like here
but this says that, at the end, W doesn't really depend on the gas temperature or reversible process crap
at the end W is simply a constant, atmospheric pressure is...
This looks like a classical setup but I can't find a solution. We can calculate the energy of the system by looking at the work done by the gravity and the spring. But how do we divide the energy between the kinetic energy of the pulley and the rotation of the pulley?
Hello
I've written that homework statement as an example to illustrate my doubt:
How can I tell if a force is conservative or not?
I've read that, if the curl of the force is 0, it's conservative. But what about the friction force (##f=\mu N##)? Its curl is also zero, but it's not conservative...
Summary:: Would energy method give us a different answer from conservation of angular momentum?
Hello,
I do not know how to type equations here. So, I typed my question in Word and attached it here. Please see photos.
Note: This question is not a homework. I did not find it in text books or...
Wikipedia says,
Unlike a free expansion , in Joule Thomson expansion work is done causing the change in internal energy. Whether the internal energy increases or decreases is determined by whether work is done on or by the fluid; that is determined by the initial and final states of the...
This problem was from the chapter on Work and Energy so, I thought of using the principle of conservation of mechanical energy. Clearly, the potential energy of the block decreases by mgh (assuming the block has mass m). This energy should have been converted to kinetic energy, but it clearly...
Diagram attached at the end
I personally think there's something wrong with this question, and I'd like if someone can tell me whether it's the question that is wrong or my approach.
If I attempt the solution thinking that M should be stationary, the solution is simple. 0 - 1/2 mv^2 = -mgh...
A recent thread posed the question whether work is done by static friction in the case of an accelerating car. Before I had a chance to reply, the thread was closed on the grounds that the subject was "beaten to death". Undaunted, I am determined to deliver the coup de grâce here with a simple...
I used work energy theorem between initial top point and point x along the incline(downwards) i got the expression of v then diffrentiated it to get a maxima but it gives me a wrong ans which is 10/6 but the actual ans is 10/3 please tell me what i did wrong
I first wrote down that 55% = Eout/Ein
I also know that W = (Facos20)(4)
and I substitute it into the first equation
55% = Eout/[(Facos20)(4)]
But i'm missing two variables here. Did i forget something or is the question missing some information?
When you say ##i = \frac{dq}{dt}## it makes sense since current is the flow of charge over time. But why was voltage defined as
##v = \frac{dw}{dq}## ? What made physicians define it in this way? Is there a mathematical way that can lead to this definition or
did they define voltage just on the...
Homework Statement: A perfect hemisphere of frictionless ice has radius R=7 meters. Sitting on the top of the ice, motionless, is a box of mass m=7 kg.
The box starts to slide to the right, down the sloping surface of the ice. After it has moved by an angle 11 degrees from the top, how much...
Homework Statement: Hetsut is the foreman of a construction project in ancient Egypt. He needs to move a giant block of stone, of mass 12 metric tons, from the docks to the temple grounds. He can go along the roads by travelling 295 meters east, then 89 meters north. Along the roads, the...
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...
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