All Questions
Tagged with kinematics work
66 questions
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How can time taken to do Work be different?
Reading about Power today, I stumbled upon this question in my mind-
"How can the time taken to do a piece of work be different in 2 scenarios?" - when I came across, the example of '2 ...
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1
answer
43
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Work Done by kinetic friction in Circular Motion
We know when an object is moving in a circular motion on a rough horizontal surface, direction of kinetic friction is constantly. Thus, fto calculate the work doen by friction, we need to use ...
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0
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1
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42
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Difference between friction force and force because of friction?
I'm doing some physics studying right now and the wording of an example question really confused me so I was hoping to get help in figuring it out. It says that " The coefficient of friction ...
0
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1
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92
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Why isn't work $Fd \sec \theta$? [closed]
In the following image if force the triangle PAN was right angle at P then the component of force in the direction of displacement would be $F\sec\theta$ so work $F*Displacement(AC)*\sec \theta $.
I ...
0
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1
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131
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Work done with varying angles
I'm having trouble understanding why work done by a force is calculated in the way as described in the following problem.
I kind of get why the work done by W is just $mgh$:
$ work = U_{1-2} = \int \...
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-1
votes
1
answer
320
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Distance-velocity relation for a body accelerated with constant power
A body of mass $m$ starting from rest from the origin ($x(0)=0$ and $v(0)=0$ at $t=0$) moves along the x-axis under the influence of a force $F$ that exerts a constant power $P$.
Question: How to find ...
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3
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57
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Work energy and power [closed]
I saw this in a textbook and I want to confirm if it's true
If a body of mass m rolls down an
inclined plane of height h and length l (hypotenuse), the work done is mgh. It is the vertical height of ...
1
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1
answer
46
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Defining Free Fall: Does Gravity Need to be the Sole Force Present?
Can a scenario be considered free fall in physics if the work done by forces other than gravity is zero, but those forces are still present? Or is it necessary for gravity to be the only force present ...
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3
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4
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550
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Does doubling speed require double the fuel or quadruple the fuel?
I'm writing a piece on the efficiency of trains versus trucks, and one of the points I was making is that trains can take advantage of not having to stop and start multiple times. This is obviously ...
2
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1
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113
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What happens if I rewrite the acceleration in work formula this way?
Work is known as
\begin{equation}
W=\vec{F}.\vec{q},
\end{equation}
thus for a gravitational force $\vec{F}_g=m\vec{g}$ we have
\begin{equation}
W=mgh.
\end{equation}
My derivation is as follows:
\...
user330731
0
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1
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55
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Question on work done and frame of reference [closed]
While solving a question which is.....
If an object is kept in a non inertial frame moving up with acceleration 'A' find the work done by pseudo force on the object taking a person standing on ground ...
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2
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Does the kinetic energy theorem imply that any body on wich is exerted the same space-dependent force is equally accelerated?
So, we have a body $P_1$ of mass $m$ that travels from $A$ to $B$ along a straight line, on wich is exerted a constant force $F$ dependent only on the position of $P_1$. We know that the work done is $...
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1
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1
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596
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Acceleration as a function of displacement
I am given a question such that a 0.280kg object has a displacement (in meters) of $x=5t^3-8t^2-30t$. I need to find the average net power input from the interval of $t=2.0s$ to $t=4.0s$.
I know the ...
- 115
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3
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154
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Question regarding work-energy theorem
The Work Energy theorem states that work $W$ done is equal to the change in kinetic energy $KE$.
$$
W= Δ{KE}
$$
But say some work I do is stored as Potential Energy, in this case, the some work done ...
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-2
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1
answer
67
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What to make out of this.....? [closed]
Let's set up an experiment first.
Suppose there is a body of rest mass $m$ at rest in an observers inertial frame and it is accelerated to almost $c$ (speed of light) at constant acceleration $a$ with ...
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4
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223
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How do we lose calories while treading on a treadmill even the displacement is 0? [duplicate]
How do we lose calories while treading on a treadmill even the displacement is 0?
Since, $W = F\cdot d$
Here $d = 0$
Hence, $W = 0$
2
votes
2
answers
177
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Work of the same force acting once on a moving object and once on a motionless one
If the same force $F$ acted once on an already moving object and once on a motionless object. would it give more energy to the moving object than to the motionless one?. Note that both objects have ...
1
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2
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512
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Why is the minimum work done not negative in this case?
I was going through my grade 10 physics textbook and noticed that $F S \cos 180^\circ$ (work done will be negative) is less than $F S \cos 90^\circ$ (work done is zero) but it is still stated that $F ...
4
votes
2
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135
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Would it be easier to break a stack of planks joined together or when they have gaps between them?
If there is a stack of n identical planks (say n=5) and we need to break them (like in karate), would it be easier (i.e. would it require less force) if they are stacked together (figure on the left) ...
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2
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6
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Where did the kinetic energy formula come from? [duplicate]
I was looking for a proof for it and all rely on the work-energy theorem. But the work energy theorem relies on the kinetic energy equation. Ergo circular logic.
So where did it come from?
2
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3
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188
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Why doesn't an initial velocity affect the final velocity?
I've been stuck on a basic kinematics problem for some time, which usually goes something like this.
Three balls are dropped from some height, $h$, with initial velocity $|v|$. Ball #$1$ is given $...
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2
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46
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Equation for Work required to achieve a certain velocity [closed]
If we are trying to find the work required to get an object moving at velocity $v$, and we start with $w = f\cdot d$, we can then make the following substitutions:
substitute $f$ with ma: $w = m\cdot ...
5
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3
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Problems regarding the equations for work done and kinetic energy
For example consider that I am driving a car with a mass of $200$ kg moving at $10$ m/s relative to an outside observer, with an assumed constant opposing friction of $50$ N, for simplicity (it won't ...
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2
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419
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Is the work-energy theorem a derivation of the motion equations and Newton's second law?
I've been studying the work-energy theorem and also how the kinetic energy formula is derived from the equations of motion. It seems like the work-energy theorem is another way to rewrite the motion ...
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2
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0
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482
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Why does my derivation of K.E seem correct but not agree with the formula of K.E? [closed]
We know that
$$\vec{F}=m\vec{a}$$
$$Work = \vec{F}\cdot\vec{S}$$ where $\vec{S}$ is the displacement.
So, we have,
$$W = m\vec{a}\cdot \vec{S} = \frac{m(\vec{v}-\vec{u})}{t}\cdot \vec{S}$$
...
- 1,043
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1
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66
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Work done in uniform circular motion? [closed]
I received this lesson earlier, and I’m struggling to understand how this works. In the image below, my physics teacher shows that there is some sort of work done over one revolution of a mass in a ...
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2
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112
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How is energy conserved in terms of "Work"
Basic equation of work is given by $F\cdot s$. When work is done, the energy is stored either in form of potential or kinetic. My question arises when we look at a case of applying $m g$ of force ...
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1
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Finding the drag force from the final velocity of a falling object
I know the velocities (v) of an object after it fell for respective distances (s). From that alone, is it possible to calculate the drag force at a specific moment in time? If not what else would I ...
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2
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581
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What is function of force $F$ and work $W$?
I know that :
Position $$r:\mathbb{R} \to\mathbb{R^3} \ \ \ \ \ ; \overrightarrow{r}(t)$$
Velocity $$v :\mathbb{R} \to\mathbb{R^3} \ \ \ \ \ ; \overrightarrow{v}(t)$$
Acceleration $$a:\mathbb{R} \...
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1
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If a box is carried 2 flights of stairs to an attic, is more work done than opposed to go straight up with a ladder? [duplicate]
The box has the same weight. I think that the stairs does more work because it travels a further distance as it is a less direct path opposed to going straight up.
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2
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Why is velocity squared in kinetic energy? [duplicate]
I'm not looking for how it's derrived. I'm wondering why it works out this way that doubling the speed quadrouples the KE.
Here's my thought process:
A car is moving down the road (ignoring air ...
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1
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1
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Using Kinematic Equations of Motion to find Velocity in Spring-Block System [closed]
Suppose a block of mass, m is connected to a spring of force constant, k. The block is moved on a frictionless surface through distance, b with the help of a uniform external force, F so that the ...
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3
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If we move from one point to another with constant speed/velocity will the work done be zero or not?
We know that work done is change in kinetic energy, but when the speed is constant the work done must be zero, I guess. Am I right or wrong?
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Particle moving on circular path, is work being done?
If a particle moves along a circular path, there is no work being done on it. Is it true or false?
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1
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Velocity is zero, but acceleration is not?
Imagine a block (of mass m) attached to a spring (of spring constant k) that is hanging from a fixed support on the ceiling. The spring is initially in its relaxed state( no compression or extension). ...
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0
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1
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Can the Kinetic Energy formula by derived using Algebra or is Calculus required [closed]
The formula for Kinetic Energy $T$ is $T=\frac{1}{2}mv^2$
I can derive this using Calculus so I don't need to be shown that.
I can also derive it using Algebra but have some issues as follows.
$$T=...
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2
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512
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Can the impulse-momentum and work-energy principles be combined?
I was curious if the work-energy and impulse-momentum principles be combined where the common factor is average Force.
Work Energy: $F_{avg} \times d = 0.5m(v_f-v_0)^2$
Impulse Momentum: $F_{avg} \...
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2
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90
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Why doesn't this formula work? [duplicate]
Let's assume that an object has KE expressed by velocity $v$ and mass $m$.
If work $w$ has been done to this object such that its new speed (same direction) is $s$. There are 2 ways(I know) to ...
user154674
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2
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70
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Human body calories consumption estimate based on physics approximation
I was looking for references online about equations that relates human kinetics and calories consumption, and it seems there are no many engineers interested in weight lifting (go figure...). I think ...
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1
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Energy required to move an object at different speeds [closed]
Does it take more or less energy to move/push a 500 pound cart over a distance of say 100 yards on a smooth surface at a speed of 5 mph versus a speed of 1 mph?
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0
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Kinetic energy vs Kinetic Energy scenario in a collision, mechanical energy used for work?
Most collisions have Kinetic energy conserved or in the case of inelastic collisions energy is lost into other forms.
Though the equation of "TMEi + Wnc =TMEf" is true
however, what if two unequal ...
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1
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1
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what is the energy required to change only direction of a vector? [closed]
Does change in velocity vector change Kinetic energy of a system?
Does any energy change when we change direction of a vector of a system?
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1
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1
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83
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Projectiles ability to do work to a box when connected by string? [closed]
I was wondering, the work-energy theorem states that KE can do work, as it is Mechanical energy.
if the KE energy and thus Mechanical energy of a ball, if external...can do work on an object, ...
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1
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a question on work and kinetic energy [closed]
A bullet has a mass of 0.02kg and is moving with a speed of 10m/s. It can penetrate 10cm of a given target before coming to rest. If the same target is only 6cm thick, what will be the speed and ...
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1
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1
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Does this count as a proper derivation of the formula for work and kinetic energy? [closed]
$v_{av}$ = average velocity,
$d$= distance,
$a$ = acceleration,
$m$ = mass
Given:
$$v_{av}*t=d$$
$$t=\frac{v_f-v_i}{a}$$
$$v_{av}=\frac{v_f+v_i}{2}$$
Then:
$$\frac{v_f+v_i}{2}*\frac{v_f-v_i}{a}=d$$
$...
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2
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3
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528
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What was the motivation behind the work formula?
Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
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3
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3
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881
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Is there an intuitive explanation of the work formula?
Upon learning calculus, I decided it was time to derive all of classical mechanics to give myself a good understanding of physics. What I found was that, while trying to do so, I would need some ...
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4
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3
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670
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How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?
After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
- 566
2
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1
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167
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Necessity of the Notion of Work and Kinetic Energy
I've worked through many example problems in my college physics text in the section on kinetic energy and work. I noticed that if the desired quantity is velocity or force, they can be solved entirely ...
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1
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Work done: kinetic energy or area under F-ds curve?
Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE.
Suppose a variable force is ...
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