All Questions
16 questions
0
votes
1
answer
42
views
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 ...
1
vote
2
answers
512
views
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 ...
2
votes
0
answers
482
views
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
-1
votes
1
answer
66
views
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 ...
- 1
1
vote
1
answer
3k
views
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 ...
- 335
0
votes
1
answer
9k
views
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). ...
- 67
0
votes
1
answer
110
views
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.
$$T=...
- 1,369
-1
votes
2
answers
90
views
Why doesn't this formula work? [duplicate]
Let's assume that an object has KE expressed by velocity $v$ and mass $m$.
If work $w$ has been done to this object such that its new speed (same direction) is $s$. There are 2 ways(I know) to ...
user154674
-2
votes
1
answer
828
views
Energy required to move an object at different speeds [closed]
Does it take more or less energy to move/push a 500 pound cart over a distance of say 100 yards on a smooth surface at a speed of 5 mph versus a speed of 1 mph?
- 1
1
vote
0
answers
63
views
Kinetic energy vs Kinetic Energy scenario in a collision, mechanical energy used for work?
Most collisions have Kinetic energy conserved or in the case of inelastic collisions energy is lost into other forms.
Though the equation of "TMEi + Wnc =TMEf" is true
however, what if two unequal ...
- 67
0
votes
1
answer
133
views
a question on work and kinetic energy [closed]
A bullet has a mass of 0.02kg and is moving with a speed of 10m/s. It can penetrate 10cm of a given target before coming to rest. If the same target is only 6cm thick, what will be the speed and ...
- 29
1
vote
1
answer
85
views
Does this count as a proper derivation of the formula for work and kinetic energy? [closed]
$v_{av}$ = average velocity,
$d$= distance,
$a$ = acceleration,
$m$ = mass
Given:
$$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$$
$...
- 566
0
votes
1
answer
854
views
Power - 1/2 Force x velocity? [closed]
A pump, taking water from a large reservoir, is used to spray a jet of water with speed 20m/s. The nozzle of the pipe has radius 0.05m, and is level with the surface of the reservoir (no change in PE)....
- 113
0
votes
2
answers
206
views
Is there a mistake in this example in my mechanics textbook?
This is a worked example in my mechanics book:
But I think this worked example is wrong. In the 6th line. shouldn't $X=4R$ as the expression for distance above the surface is $(X-R)$ and when the ...
- 2,177
3
votes
2
answers
8k
views
Increase in velocity by loss of mass? [closed]
A trolley of mass 300kg carrying a sand bag of 25kg is moving uniformly with speed of 27km/h on a frictionless track. After a while, sand starts leaking out of a hole on the floor of the trolley at ...
- 300
1
vote
2
answers
4k
views
Calculating force required to stop bungee jumper
Given that:
bungee jumper weighs 700N
jumps off from a height of 36m
needs to stop safely at 32m (4m above ground)
unstretched length of bungee cord is 25m
Whats the force required to stop the ...
- 495