What is Newton's laws: Definition and 478 Discussions
In classical mechanics, Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, unless it is acted upon by an external force. The second law states that the rate of change of momentum of an object is directly proportional to the force applied, or, for an object with constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration. The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object.
The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems, which laid the foundation for Newtonian mechanics.
Homework Statement
a)If the mass of the crate is doubled but the initial velocity is not changed, what distance does the crate slide before stopping? Explain.
b) If the initial velocity of the crate is doubled to 2vi but the mass is not changd, what distance does the crate slide before...
Homework Statement
A crate pushed along the floor with velocity Vi slides a distance d after the pushing force is removed.
a)If the mass of the crate is doubled but the initial velocity is not changed, what distance does the crate slide before stopping? Explain.
b) If the initial...
Homework Statement
1)The particle shown below is at rest, where F = 65.0 N, and θ = 33.1°. Find the magnitudes of F1 and F2.
2)Just after opening a parachute of negligible mass, a parachutist of mass 99.5 kg experiences an instantaneous upward acceleration of 1.09 m/s2. Find the force...
Homework Statement
A railway engine pulls two carriages of equal mass with uniform acceleration. The tension in the coupling between the engine and the first carriage is T. Deduce the tension in the coupling between the first and second carriages.
Homework Equations
The Attempt at...
Homework Statement
The two blocks shown in the diagram are at rest on a horizontal surface when a force P is applied to block B. Blaocks A and B have masses 20kg and 35kg respectively. The coefficient of friction between the two blocks is 0.35 and between the horizontal surface and Block B is...
Hey all, here's a question from one of my homework sets, any help is greatly appreciated.Homework Statement
I've included a diagram of the situation. Basically, I have to find out how long it takes the block to reach the end of the ramp, the spring is massless, and friction is a factor in this...
1. What is the weight of an astronaut during lift off, if his actual weight is 750N and the acceleration of the craft is 5g's.
The way I tried to solve it:
F=ma
F= 75(50)
But answers are not matching, as the answer should be 4500N.
I think I am missing something with that has to do with...
Homework Statement
The coefficient of friction between the block of mass m1 = 3.00 kg and the surface in the figure below is μk = 0.335. The system starts from rest. What is the speed of the ball of mass m2 = 5.00 kg when it has fallen a distance h = 1.45 m?
Homework Equations...
A bullet of mass 20g strikes a fixed block of wood at a speed of 320 m/s. The bullet embeds itself in the block of wood, penetrating to a depth of 6.0 cm. Calculate the average net force acting on the bullet while it is being brought to rest
Homework Statement
Sam, whose mass is 75 kg, straps on his skis and starts down a 50-m-high, 20 degree frictionless slope. A strong headwind exerts a horizontal force of 200 N on him as he skies.
Find his speed at the bottom of the slope using Newton's Law
Find his speed at the bottom...
Here is a copy of my notes on the motor. Basically it's just some of Newton's Law of Rotation combined with Kirchoff's Laws. Then we put the model into state space form.
Could someone just please explain to me the meaning of the equations? It's been a while since I've had physics. Thanks a...
Homework Statement
The 100 kg blcok in the figure takes 5.40 s to reach the floor after being released from rest. What is the mass of the block on the left?
Homework Equations
F=ma
sf=si + (1/2)(a)(delta t)
The Attempt at a Solution
I know to find acceleration you use
sf=si +...
Homework Statement
To move a large crate across a rough floor, you push on it with a force F at an angle of 21°, below the horizontal. Find the acceleration of the crate, given that the mass of the crate is m = 28 kg, the applied force is 322 N and the coefficient of kinetic friction between...
Homework Statement
A 1420 kg jet engine is fastened to the fuselage of a passenger jet by just three bolts (this is the usual practice). Assume that each bolt supports one-third of the load.
(a) Calculate the force on each bolt as the plane waits on line for clearance to take off.
(b)...
Hi, it is known that all bodies moving with a velocity will remain moving with a constant velocity unless a force is applied to a body. (according to Newton's laws). But I thought about this:
F = Ma. But if we had a very very very very small object (hypothetically), we could virtually take...
Homework Statement
A 5.10 kg instrument is hanging by a vertical wire inside a spaceship that is blasting off at the surface of the earth. This ship starts from rest and reaches an altitude of 290 m in 10.0 s with constant acceleration.
a.) Draw a free-body diagram for the instrument...
Personally I'm on the border-line between atheist and agnostic however the following statement gets me thinking. It is a statement that every physicist can resite without having to think;
"Every object remains in a state of rest or in uniform motion until acted on by an external force"...
Newton's laws cannot be proven!
As far as i know, Newtons laws are...
1st Law-- A body at remains at rest and a body at uniform motion remains at uniform motion unless an external for acts on it.
2nd Law-- F=ma
3rd Law-- Every action has an equal and opposite reaction.
No method has...
Homework Statement
A person pushes a 14.0-kg lawn mower at constant speed with a force of F= 88.0N directed along the handle, which is set at an angle of 45 degrees to the horizontal. (a) Draw the free-body diagram showing all forces acting on the mower. Calculate (b) the horizontal friction...
Homework Statement
A person stands on a scale on an elevator. If the mass of the person is 96.34 kg and the elevator travels upward at a constant speed of 4.42 m/s, what is the reading on the scale?
Homework Equations
m = 96.34 kg
V avg = 4.42 m/s
The Attempt at a Solution
I...
Homework Statement
8. (II) A car can decelrate at -4.80 m/s^2 without skidding when coming to rest on a level road. What would its decelration be if the road were inclined at 13 degrees uphill? Assume the same static friction force.
Homework Equations
Ffr = MuFn
F = ma
The...
Homework Statement
A 65kg swimmer jumps of a 10m tower.
a) Find the swimmer's velocity when hitting the water
b) The swimmer comes to a stop 2.0m below the surface. Find the net force exerted by the water.
Homework Equations
F=ma?
I don't know the rest, which is part of the problem...
Homework Statement
A block of mass m lies on a wedge of mass M as shown in figure. Answer the following parts separately.
(a) - With what minimum acceleration must the wedge be moved towards right horizontally so that the block m falls freely?
(b) - Find the minimum friction co-efficient...
Homework Statement
Three crates are arranged. Their masses are m1=29.8, m2= 15.3, m3= 27.3. The applied force of 910 N is directed horizontally and the coefficient of friction is u= .277
WHAT IS THE MAGNITUDE OF THE CONTACT FORCE BETWEEN M1 and M2?
WHAT IS THE MAGNITUDE OF THE CONTACT...
Homework Statement
A 1380kg car is moving due east with an initial speed of 27 m/s . after 8.00s the car has slowed down to 17.0 m/s . Find the magnitude and direction of the net force that produces the deceleration
Homework Equations
Net force of x= MAx
Net force of y= MAy
The...
I'm having a lot of trouble trying to figure out some of these problems. If people could help me, it'd be greatly appreciated!
1. A 50.0-kg person takes a nap in a backyard hammock. Both ropes supporting the hammock are at an angle of 15.0° above the horizontal. Find the tension of the ropes...
Homework Statement
Some people believe that the Moon controls their activities. The Moon moves from being directly on the opposite side of Earth from you to be being directly overhead. Assume that the Earth-Moon (center-to-center) distance is 3.82 multiplied by 108 m and Earth's radius is 6.37...
Homework Statement
A 0.54kg ball falls from rest at a height of 26m and rebounds up 16m. If the contact between the ball and ground lasted 1.8ms, what average force was exerted on the ball?
Homework Equations
F=ma
v²=v0²+2a(x-x0)
v=v0+at
1000ms=1s (1.8ms is 0.0018s)
The Attempt at...
Homework Statement
A train is traveling up a 3.73 degrees incline at a speed of 3.25 m/s when the last car breaks free and begins to coast without friction.
a) How long does it take for the last car to come to rest momentarily?
b) How far did the last car travel before momentarily coming to...
Homework Statement
"Blocks A, B, and C are placed as in the figure and connected by ropes of neligible mass. Both A and B weigh 25.0 N each, and the coefficient of kinetic friction between each block and the surface is 0.35. Block C descends with constant velocity. a) Draw separate free body...
Projected Up an Incline A block is projected up a frictionless inclined plane with initial speed v1 = 3.43 m/s. The angle of incline is θ = 32.5°.
(a) How far up the plane does it go?
(b) How long does it take to get there?
(c) What is its speed when it gets back to the bottom...
Homework Statement
An 81 kg man lowers himself to the ground from a height of 10.6 m by holding onto a rope that runs over a frictionless pulley to a 60 kg sandbag.
(a) With what speed does the man hit the ground if he started from rest?
(b) What can he do to make him hit the ground slower...
First post =]
Requesting guidance with this particular problem:
Homework Statement
A 1.20 kg object is moving in the x direction at 14.4 m/s. Just 3.31 s later, it is moving at 28.8 m/s at 34.0 degrees to the x axis.
a.) What is the magnitude of the force applied during this time...
Homework Statement
A worker pulls horizontally on a rope that is attached to a 10 kg crate that is resting on a rough floor. The coefficients of static and kinetic friction are 0.5 and 0.3 respectively. The worker pulls with a force of 45N. What is the frictional force exerted by the...
A fisherman is fishing from a bridge and is using a "32.0-N test line." In other words, the line will sustain a maximum force of 32.0 N without breaking. What is the weight of the heaviest fish that can be pulled up vertically, when the line is reeled in with an acceleration whose magnitude is...
A toboggan slides down a hill and has a constant velocity. The angle of the hill is 8.80 with respect to the horizontal. What is the coefficient of kinetic frction between the surcae of the hill and the toboggan?
So i used the formula: sum of forces(x)= cos (8.80)=0.98823
Forces (y)=...
Homework Statement
A bug flies into the windshield of a big rig that is traveling on the freeway. What type of collision is this? Is momentum conserved? Is energy conserved? What force does the bug exert on the windshield (make a statement about Newton’s 3rd Law)?
Homework Equations...
Homework Statement
A tree house has a vertical "fire pole" of smooth metal, designed for quick exits. A child of mass 35.7 kg slides down the pole with constant acceleration, starting from rest. The pole is 3.10m high. The journey to the ground takes 2.00s.
a) what is the magnitude of the...
Newton's Laws -- friction, tension, acceleration
A block of mass m1 = 2 kg and a block of mass m2 = 3 kg are tied together and are pulled from rest across the floor by a force of Fp = 24 N. The coefficient of friction of the blocks with the floor is μ = 0.27.
a) What is the acceleration of...
Homework Statement
The figure shows two blocks connected by a cord (of negligible mass) that passes over a frictionless pulley (also of negligible mass). The arrangement is known as Atwood's machine. Block 1 has mass m1 = 0.900 kg; block 2 has mass m2 = 2.70 kg. What is the tension in the...
Homework Statement
Part 1
Two blocks are in contact on a frictionless table. A horizontal force F is applied to M2, as shown. If M1 = 1.03 kg, M2 = 3.40 kg, and F = 5.10 N, find the size of the contact force between the two blocks...
Suppose the cord in Fig. 4-22 is a heavy rope of mass 1.0 kg. Calculate the acceleration of each box and the tension at each end of the cord, using the free-body diagrams shown in Fig. 4-46. Assume the cord doesn't sag. (m1 = 10.5 kg , m2 = 12.5 kg and FP = 35.0 N)
m1 stands for the mass of...
1. A car coasts (engine off) up a 30 degree grade. If the speed of the car is 25 m/s at the bottom of the grade, what is the distance traveled before it comes to a rest?
2. mostly my class so far has dealt with equations calculating work and force by drawinf free body diagrams and using...
Homework Statement
1) A freight train has a mass of 1.5 x 10^7 kg. If the locomotive can exert a constant pull of 7.5 x 10^5 N, how long does it take to increase the speed of the train from rest to 80 km/h?
2) A 5.0 g bullet leaves the muzzle of a rifle with a speed of 320 m/s. What force...
Homework Statement
A 4.0-kg toboggan rests on a frictionless icy surface, and a 2.0 kg block rests on top of the
toboggan. The coefficient of static friction µs between the block and the surface of the toboggan is 0.60, whereas the kinetic friction coefficient is 0.51. The block is pulled...
Homework Statement
A 4.1-kg box is pushed along a horizontal floor by a force of magnitude 21 N at an angle θ = 35° with the horizontal. If the coefficient of kinetic friction between the block and the floor is 0.20, calculate the acceleration of the box. Be careful when calculating the...
Homework Statement
A cup of coffee is sitting on a table in an airplane that is flying at a constant altitude and a constant velocity. The coefficient of static friction between the cup and the table is 0.30. Suddenly, the plane accelerates, its altitude remaining constant. What is the maximum...
Homework Statement
A train consists of of 50 cars, each of which has a mass of 6800 kg. The train's acceleration = 0.08 m/s(squared). Ignore friction and determine the tension in the coupling (a) between the 30th and 31st cars and (b) between the 49th and 50th cars.
Homework Equations
Net...
Homework Statement
A large gun accelerates a 5.0 kg mass from rest to a speed of 4000 m/s into orbit. The net force accelerating the bullet is 490,000 N.
How long will it take the projectile to come up to speed?
It doesn't say anything above air resistance or gravity.
Homework Equations...