# Read about newton's second law | 24 Discussions | Page 1

1. ### I Alternative approach to analyzing a massless string

Consider a massless string which can rotate about a fixed pulley (first picture). The coefficient of static friction is μ. Assuming that the motion is impending, the goal is to find the equation that describes the variation in tension of the string. ( T2/T1 = eμΦ where Φ is the subtended angle.)...
2. ### B Body force vs Inertial force

Hello everyone. This is my first time on the physics forum, but I think I'm going to be a regular here. I was reading a paper that outlined various ways to approach solving dynamic problems. The first approach outlined by the author is D'Alembert's principle of virtual work. In describing...
3. ### Newton's Second law

Homework Statement The two forces F⃗ 1 and F⃗ 2 shown in (Figure 1) act on a 29.0-kg object on a frictionless tabletop. Suppose that F1 = 10.8 N , and F2 = 19 N . A. Determine the magnitude of the net force on the object for the diagram (a) in the figure. B.Determine the angle between the...
4. ### B Problem - Different weights on a swinging rod

The following problem is from Sears and Zemansky's textbook. A wooden rod of negligible mass and length 80.0 cm is pivoted about a horizontal axis through its center. A white rat with mass 0.500 kg clings to one end of the stick, and a mouse with mass 0.200 kg clings to the other end. The...
5. ### Finding the speed of a book against a vertical wall

Homework Statement the main question asks: "If the book is initially at rest, what is its speed after it has traveled 0.400 m up the wall?" Homework Equations ∑F = m*a vf2 = vi2 + 2 * a * d , when initial velocity is 0. The Attempt at a Solution So here's my free body diagram: and out of...
6. ### B F=mg or F=-mg?

Hi everyone! I'm really sorry if I'm using the wrong forum. It's my first time at PF. I'm pretty new to physics, as I began studying it just two years ago, but I'm really interested in the subject of astrophysics so I bought myself and started reading 'Introduction to rocket science and...
7. ### Force required to negate vertical acceleration with friction

Homework Statement Two blocks m (16kg) and M (88kg) are as shown in the figure. If the co-efficient of friction b/w the blocks is 0.38 but the surface beneath the block is frictionless, what is the minimum force required to hold m against M? Homework Equations Fnet = ma Fs = μs*Fa The...
8. ### Bobseld Forces Problem

Homework Statement In the men's four-man bobsled event in the winter olympics, the maximum mas of a bobsled with pilot, two riders, and a brakeman is 630 kg. During a practice run, the rear rider and the brakeman exert average forces of 1220N and 1200N [forward] respectively to accelerate a...
9. ### Help with Forces, Pulleys, and Whether People get pulled

Homework Statement A rope of negligible mass passes over a pulley of negligible mass attached to the ceiling, as shown above. One End of the rope is held by Student A of mass 80 kg, who is at rest on the floor. The opposite end ofthe rope is held by Student B of mass 70 kg, who is suspended at...
10. ### Meaning of y-int. on graph of acceleration vs. hanging mass

Homework Statement In an experiment, I measured the effect of mass on the acceleration of a cart, rolling down a leveled air track. I then graphed acceleration vs. mass (m'), where: m' = m / (M+m); M = mass of the cart, m = hanging mass, which was increased with subsequent trials. Homework...
11. ### Determining velocity for a pulley/rope system

The Question: Using a simply pulley/rope system, a crewman on an Arctic expedition is trying to lower a 5.65-kg crate to the bottom of a steep ravine of height 23.9 meters. The 60.9-kg crewman is walking along holding the rope, being careful to lower the crate at a constant speed of 1.50 m/s...
12. ### Newton's Second Law. Involving an airplane.

Homework Statement An airplane goes into a turn 3.6km in radius. If the banking angle required is 28 degrees from the horizontal, what is the plane's speed? Homework Equations Newton's Second. The only forces acting on the plane are gravity and the normal force. This isn't given in the...
13. ### Tension in string in system with multiple objects?

Homework Statement I am stuck on this problem: So the question is asking for F21, F12, F32, and F23. (That's the force by 2 on 1). The mass of m2 is variable. There are four cases where I need to solve for the forces: when m2 has mass of 3kg, 0.3kg, 0.03kg, and 0kg. The mass of m1 = 2.5kg, the...
14. ### Dynamics Problem -- box accelerated horizontally via a mass & pulley system

Homework Statement A 1.0 kg box on a horizontal frictionless surface is accelerated by attaching a 1.5 kg mass as shown in the diagram. What is the magnitude of acceleration of the box?(Remember, both boxes accelerate.) Homework Equations F = ma The Attempt at a Solution I drew a free body...
15. ### Conceptual Newton's Law's Questions - HS Freshman Physics

NOTE: The following questions are not part of any homework assigned. This is part of finding extra concept-related questions to help me study for my physics unit test. Homework Statement I have conceptual questions, not problems. I'll provide sufficient evidence that I've attempted to think...
16. ### Friction and force help

Homework Statement Three blocks in contact with each other are pushed across a rough horizontal surface by a 98 N force as shown. The acceleration of gravity is 9.8 m/s^2. ----F--->|2kg| |7.7kg| |9.2kg| u = 0.082 If the coefficient of kinetic friction between each of the...
17. ### Are *two* external forces always required to cause rotation?

As the title says, can there be any rotation if only one force is applied to an object at rest. For instance, if I had a rod laying flat on a frictionless surface, and I pushed one end, am I correct to say that Newton's second law says that all of that force goes into acceleration the center of...
18. ### Calculating force from distance traveled and initial speed of projectile

Homework Statement Estimate the average force exerted by a shot-putter on a 7.0-kg shot if the shot is moved through a distance of 3.0m and is released with a speed of 10m/s . Homework Equations F=ma Maybe the Five Equations for constant acceleration? The Attempt at a Solution So my guess is...
19. ### What did I do wrong? (Newton's Second Law)

Homework Statement (This is a problem I made up, so if the problem is with the problem, let me know.) A 500N ball is being pushed down a carpeted decline of 24° to the horizontal. It starts from 1 m/s and ends the 20 foot (6.1 m) decline at 32 m/s. What is the coefficient and force of kinetic...
20. ### Can you find the applied force with just the initial and final velocties?

Homework Statement I'm trying to create a problem for my physics standards that is hard. I gave myself a ball being pushed down a carpeted decline at 24° from the horizontal. The balls starts with an initial velocity of 1 m/s and ends the 6 meter decline at 5 m/s. I want to find the applied...
21. ### Why is force invariant in Newtonian mechanics?

Recently, I've been pondering deeply on relativity (both Galilean and SR) and all of a sudden I find that I don't grasp even the basic concepts of physics (or life) anymore, i.e. I can't go back to my previous, "normal" mode of thinking. Consider Newtonian mechanics, take the ground to be at...
22. ### Newton's second law with vectors

Homework Statement A 9 kg object is subjected to two forces, http://www.webassign.net/images/Farrowbolditalic.gif1 [Broken] = 7 N i - 4 N j and [PLAIN][PLAIN]http://www.webassign.net/images/Farrowbolditalic.gif2 [Broken] = 7 N i - 9 N j. The object is at rest at the origin at time t = 0. (a)...
23. ### Newton's 3 Laws Problem

Homework Statement The 20.0 kg box is being pushed with a 45.0N Force acting at an angle of 25.0*. The coefficient of kinetic friction on this surface is 0.150. Find the acceleration Homework Equations F=ma Fy=0 Fx=0 The Attempt at a Solution So I attempted this so far (sum)Fy=0 Py+Fn-Fg=0...
24. ### Magnitude of a ball's Acceleration

Homework Statement A 0.17-kg cue ball rests on the pool table. It's struck by a cue stick applying force F1→ = 13Ni^+21Nj^ Determine the magnitude of the ball's acceleration. Homework Equations ax = Fnet, x / m ay = Fnet, y / m a = Fnet / m The Attempt at a Solution Components of...