In physics, a force is any influence that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newton (N). Force is represented by the symbol F (formerly P).
The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.
Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the internal mechanical stress. Such internal mechanical stresses cause no acceleration of that body as the forces balance one another. Pressure, the distribution of many small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of solid materials, or flow in fluids.
Homework Statement
The original question was to find the value of the angle between PA and AB. I have a certain idea regarding how to find it, but first I have to identify all forces acting on the system and their directions. So, I would be grateful if someone can explain how the frictional...
Homework Statement
I've encountered a question about electrostatic forces on vertices of an equilateral triangle and I believe that I solved it correctly but my Physics teacher has marked it as incorrect. Am I correct? Amy clue why my Physics teacher marked it wrong? This is the question and...
Homework Statement
For this problem , i found that the internal force AB at point A and point B pointed in the same direction ( as shown) in my working , so , how they cancel off each other ?Since they can't cancel off each other , so they are not stable , right ? The structure is statically...
Homework EquationsThe Attempt at a Solution
[/B]
I was of the understanding that the slope can be calculated as mgsin20 whereas the force acting straight down through the lift is mgcos20 but the answer is mg divided by cos 20??
Homework Statement
The following circuit is given.
I intend to calculate the current in every resistor (every quantity except i1, i2, i3, is known).
My textbook states that ℰ3-ℰ1 = (R1+R2+R3+R4+2r)*i, but I think it should be -ℰ3+ℰ1 on the left-hand side, since the current enters the negative...
so a pilot is spining in a circle at a constant speed, the g forces he will feel will be the same than normal acceleration dependant on wr
but now you put him inside a tube where he can move along varying the radius of the circle
now the normal acceleration will be zero because he is in the...
Homework Statement
The single moon of an Earth-like planet creates tides on the planet that are slowing the planet’s rotation. The planet’s rate of rotation is decreasing at a rate of 7.00 x 10-7 radians/sec/century. The mass of the planet is 6 x 1024 kg, and its diameter is 12,600 km. The...
Homework Statement
The 5.7 N weight is in equilibrium under the influence of the three forces acting on it. The F force acts from above on the left at an angle of α with the horizontal. The 5.2 N force acts from above on the right at an angle of 63◦ with the horizontal. The force 5.7 N acts...
Homework Statement
In my AP Physics class we need to design a loop that pulls around 4 G's. From what I understand, the diameter of the loop must be 2/5 times the initial drop. I cannot seems to get the G forces around 4. Any help? I found that the Clothoid loop reduces G forces but I can't...
Hello
I have a question about the explanation given for the attached image about the balanced ladder on a wall. At the end the sentence says that, "Consequently the frictional force F at A passes through O". I am not able to understand why this is so. Can anybody please shed light on this...
Homework Statement Is it possible to find the VA , VB and VC without ' breaking ' the beam into 2 parts ?
Homework EquationsThe Attempt at a Solution
Here's my working , i gt
Moment about A = 10(1) -VB(2) -VC(4) +5(3)(4 + (3/2) ) = 0 Hence , 92.5-2VB -4VC= 0
moment about B = VA(2) -10-VC(2)...
Homework Statement
sorry, me again.
The following figures show various forces acting on gliders of various masses at rest on a frictionless track. In each case, the force is applied for 30cm. The choice listing the examples in decreasing order for the increase in kinetic energy is {-4J < -2J <...
Homework Statement
If the incline of the driveway is 19 ∘ from the horizontal, what must the minimum coefficient of static friction be between your shoes and the ice?
Homework Equations
Fs=uN
The Attempt at a Solution
Tidal Forces: "It arises because the gravitational force exerted by one body on another is not constant across it". which implicitly implies that the acceleration is not constant on that body.
Equivalence Principle: "weightlessness sensation occurs when one free falls in gravity" - which...
I was watching the following TED Talks video about using carbon nanotubes to build a space elevator:
After the 12-13 minute point the speaker starts describing how very short carbon nanotubes can be pulled from a "nanotube forest" and spun together to create a very long thread. However the...
Homework Statement
A(n) 895 N crate is being pushed across a level floor by a force of 397 N at an angle of 21◦ above the horizontal. The coefficient of kinetic friction between the crate and the floor is 0.24. The acceleration of gravity is 9.81 m/s.
What is the acceleration of the box...
As far as I know, we regard the electromagnetic force, gravity, strong and weak interactions as the four fundamental forces.
We know that Newton's law of gravitation does not perform as well as Einstein's general relativity. Scientists are now using energy-stress tensor to describe...
Hi,
If you had a sealed round bottomed flask on some lab scales and you recorded the mass and then you removed all the air with a vacuum pump and then found the mass of the flask again would the difference between the two readings really be an estimate of the mass of the gas in the flask? The...
Hello all,
You all have always kindly helped me as I remember questions I have accumulated since high school days, and have never been answered. Eventually I gave up and forgot them, but as I grow old for some odd reason these things pop back up in my mind, like old ghosts from 35 years ago...
Homework Statement
"A 1.50 kg object hangs motionless from a spring with a force constant of k = 250 N/m. How far is the spring stretched from its equilibrium length?"
Homework Equations
F = -kx
W = mg
The teacher said to call the force the spring pulls up with FT.
The Attempt at a Solution...
This example is written in several books, that is if you strike a ball against a wall it applies an action force on the wall and the reaction force from the wall is the reason for the ball bouncing back..Now i have a question here that when you throw the ball, you accelerate it upto some...
Homework Statement
A tugboat pulls two barges down the river. The barge connected to the tugboat, carrying coal, has an inertia of 2.0 × 105 kg, and the other barge, carrying pig iron, has an inertia of 3.1 × 105 kg.The resistive force between the coal barge and the water is 8.0 × 103 N, and...
My textbook says that for a central force at the origin, the angular momentum is constant, because the derivative rxF is zero since F points radially outwards so it is in the same direction as r. Ok, but what about the angular momentum about a point other than the origin, or the angular momentum...
Homework Statement
A burst of compressed air pushes a pellet out of a blowpipe. The force exerted by the air on the pellet is given by F(t)=F0e(−t/τ), where τ is called a time constant because it has units of time.
What does F0 represent?
Homework Equations
F0 represents the maximum force...
Homework Statement
System comprised blocks, a light frictionless pulley and connecting ropes (see diagram). The 9.0kg block is on a perfectly smooth horizontal table. The surfaces of the 12kg block are rough, with μk = .2 between the two blocks. If the 5.0 kg block accelerates downward when it...
Homework Statement
Two forces act on a 55 kg object. One has a magnitude of 65 N directed 59 degrees clockwise from the pos. x axis. The other has magnitude 35 N at 32 o clockwise from the pos. y axis.What is the acceleration of the object?
The answer is given as 1.1 m/ s squared,
(I got a...
Homework Statement
A 2.34-kg cart on a long, level, low-friction track is heading for a small electric fan at 0.22 m/s . The fan, which was initially off, is turned on. As the fan speeds up, the magnitude of the force it exerts on the cart is given by at2, where a = 0.0200 N/s2. What is the...
Homework Statement
A 5.0-kg block suspended from a spring scale is slowly lowered onto a vertical spring.
Part A: What does the scale read before the block touches the vertical spring?
(answer =49.1N)
Part B: If the scale reads 32 N when the bottom spring is compressed 30 mm, what is k for...
Homework Statement
A group of construction workers are building a house and want to lower down an excess bundle of 1400 kg bricks to ground. They tie one end of a rope to the bundle of bricks, loop it through a pulley, and tie the other end of the rope to a toolbox. If the coefficient of...
Homework Statement
A 0.140kg baseball traveling 35.0 m/s strikes the catcher's mitt, which in bringing the ball to rest, recoils backward 11.0cm. What is the average force applied by the ball on the glove
Homework Equations
F=ma; FAB=-FBA
The Attempt at a Solution
Not sure where to start for...
Hi,
I don't really get what the point of volume forces is, if electromagnetism is a volume force. Its obviously no surface force, but in my opinion the definition says that its no volume force as well. The link below describes volume forces as "a force acting on all particles (volume elements)...
Homework Statement
When a wood shelf of mass 7.7 kg is fastened inside a slot in a vertical support as shown in (Figure 1) , the support exerts a torque on the shelf. Assume that the slot exerts two vertical forces on the shelf, at points A and B.
Determine the force exerted on the shelf by...
Homework Statement
a pendulum of mass m and length L is pulled back an angle of θ and released. After the pendulum swings through its lowest point it encounters a peg α degrees out and r meters from the top of the string. The mass swings up about the peg until the string becomes slack with the...
Homework Statement
I just can't seem to find anything that I can relate to for solving this problem and it's giving me a headache.
I don't even know how to start solving this question. Please help:
A man drags a package across the floor with a force of 40 N. The mass of the package is 10 kg...
If for say, I had a ''perfect object'' (Only mass with no dimensions) and I put three non-parallel and different pulling forces on the item, would these cancel themselves? After the doing the experiment myself with a non-perfect item, it seemed there was a slight advancement. The addition of the...
This is not a specific homework problem. It is a lack of understanding in theory relating to a lab report I have to write.
We (my group and I) wrapped a 40 cm PVC pipe in copper wire (very densely and for almost the entire length), applied a current to it, and dropped a permanent magnet...
Homework Statement
So we have 65N @ 30*, 30N @ 180* and 20N at 250*
Homework Equations
Ncos(angle)i + Nsin(angle)jThe Attempt at a Solution
Using this video
I did the following.
F1(65N) = 65cos(30)i+65sin30i
Then using the radian circle I saw that 30* has x,y coordinates of sqrt3/2...
Alright, so after looking at this video to do it
I did the following.
F1(65N) = 65cos(30)i+65sin30i
Then using the radian circle I saw that 30* has x,y coordinates of sqrt3/2 and 1/2 respectively. So as shown in the video I did
65(root3/2)i+65(1/2)j
= 56.3i + 32.5j
I did this for the...
Homework Statement
Problem # 1
Homework Equations
Work done by several forces
w=f * d cos theta
w=mg
n=w
The Attempt at a Solution
I can't figure out how to solve a) and b)
NOT SURE:
so my attempt a) f = mg = 30kg*9.8m/s^2 = 294N =magnitute of the force must the worker apply.(NOT SURE)...
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...
I'm trying to understand couples, moments and forces. I know that a moment is a force causing a rotation about a certain point/axis. And I know a couple is a vector that represents the... and then that's where I'm trying to get clarification.
Is a couple vector a representation of the general...
Homework Statement
Hi, I have this problem:
For motion under a pure (rest mass preserving) inverse square law force f = −αr/r3 , where α is a constant, derive the energy equation γmc2 − α/r = constant.
Homework Equations
E = γmc2
dE/dt = f.u for a pure force
The Attempt at a Solution
I...
Homework Statement
During class, we were considering position dependent forces and we used the following differential equation to describe what is happening to the object in this case:
m*(d2x/dt2) = F(x) (i.e. ma=F(x))
Then, we were introduced the potential V(x) which we defined as:
F(x) =...
Why do conservative forces conserve mechanical energy while non conservative forces do not?
According to me,
What makes the conservative forces path independent is that for a particular case they always act in a fixed direction irrespective of the direction of motion of the object on which they...
hello :)
my question is about a solved example in gregory's book
first of all , assuming that that a cylinder with radius "a" is rolling without slipping towrad the y direction in an incline plane
with angle θ with the horizon and the cylinder him self is rotating with angle Φ about him self...
A ship is being pulled by tugboats with forces of 300 N and 800 N. The angle between the forces is 45 degrees.
My question is how can we find the angle between the force vectors and the x-axis? Would it just be 45/2 =22.5 degrees or would it be different because the forces have different...
I've lately began working with Newtons laws problems at school again, and I've already ran into a few problems.
When making calculations and solving problems, it is often nessecary to understand when forces are equal to zero, and when they are not. Since every force has an equal and opposite...