Resistive force Definition and 39 Threads

[FONT=times new roman]Statement from the text : [FONT=times new roman]I copy and paste the portion of the text that am struggling to understand and underline in red the claim the author makes which I can't believe to be true. Doubt : As you can read in the first line of the paragraph and in...

i don´t understand the question

First and foremost, thank you so much for your help! I'm new to Physics Forums, and this is my first post. I thought I understood the problem, but as I moved on to the subsequent parts of it became apparent that I was missing something. I set up my ##F = ma## equation as below, and solved that...

lets say a hammer of 0.5kg strikes a nail at 10m/s. The nail penetrates into the wood by 1cm. The reason why the nail stops is because friction has eventually overcome the nails momentum. The retardation of the nail can be worked out, but Can you calculate the force that stops the nail if you...

I tried getting to the solution by the principle of conservation of energy. What goes in, must go out. If the final velocity, ie. the final kinetic energy is lower than what we started with, that energy difference must've been used to overcome the friction that lasted over some distance L...

Homework Statement Consider a rocket subject to a linear resistive force, $$f = -bv$$, but no other external forces. Use Equation (3.29) in Problem 3.11 to show that if the rocket starts from rest and ejects mass at a constant rate $$k = -\dot{m}$$, then its speed is given by: $$v =...

What would happen if a car is driving down a highway at 80Mph and one of the doors is fully opened. Will it make a big change and make it slow down or start turning?

Homework Statement A block of mass ##m = 1.00 kg## is being dragged through some viscous fluid by an external force ##F = 10.0 N##. The resistive force can be written as ##R = -bv##, where ##v## is the speed and ##b = 4.00 kg/s## is a phenomenological constant. You may ignore gravity (we...

1. Homework Statement In a theme park ride, a cage containing passengers falls freely a distance of 30 m from A to B and travels in a circular arc of radius 20 m from B to C. Assume that friction is negligible between A and C. Brakes are applied at C after which the cage with its passengers...

Consider the 1d motion of a body under the influence of the force given by F = -m*γ*vα. m is mass, γ is a constant of appropriate dimension, v is velocity and α is dimensionless constant. The value of α for which the motion will come to a stop in finite time is to be calculated. I solved the...

Homework Statement Homework Equations [/B] The Attempt at a Solution a) I'm not sure how to calculate speed without having both distance and time but I believe it will revolve around calculating gravitational potential energy and kinetic energy. bi) I think this is just simply using the...

Homework Statement A crane is slowly lifting a large box of mass 2 kg by means of a thick (but massless) rope, from the ground to a height of 10.0 m. a) How much work does the crane do on the box? How much work does gravity do on the box? b) The rope suddenly breaks and the box falls to...

Straight from my physics textbook: For objects moving at high speeds through air, such as airplanes, skydivers, cars, and baseballs, the resistive force is reasonably well modeled as proportional to the square of the speed. In these situations, the magnitude of the resistive force can be...

Hi, Imagine a boat with a skier behind it (connected with a rope). Mass of boat=2000Kg Mass of skier=80Kg At 20m/s the boat engine has a power output of 140kW Calculate the total resistive force. Power=FxV 140000W=Fx20m/s F=7000N Is the answer right ? I doubt my answer, even if its really...

Hi everyone! I posted this in the ME section as well but thought this would be a good section as well. I am working on a thesis project and have a question for anyone who feels they can answer it. I am trying to find the resistive force created when a magnet moves along a coil of wire. I have...

Hi everyone! I am working on a thesis project and have a question for anyone who feels they can answer it. I am trying to find the resistive force created when a magnet moves along a coil of wire. I have put pictures below but here is the short explanation: The pendulum, which is fixed at a...

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A water skier of mass m is pulled at a constant velocity v by a boat of mass M. Tension in the rope held horizontally by the skier is T. a) Find the total resistive force by the water and air on the skier. b) How much upward force does the water exert on the skier?What equation would I use to...

I have been working on the following question. I have finished part (a) and (b) and checked the answer. But I'm confused by the answer of part(c). A metal stake of mass 2kg is driven vertically into the ground by a blow from a sledgehammer of mass 10kg. The sledgehammer falls vertically on to...

Homework Statement A horse is pulling a canal boat using a rope at 12° to the direction of motion of the boat. The tension in the rope is 1150 N. (a) The canal boat is moving at a steady speed. Calculate the resistive force opposing the boat’s forward motion. Homework Equations...

Homework Statement On Land, a 5000kg amphibious vehicle can accelerate from rest to 10 m/s in 25 sec. Find... a)Final Kinetic Energy? -250,000 b)Avg Power furnished by engine during acceleration? -10,000 c)If the same power is required to propel the vehicle through water at a...

Homework Statement A skier of mass 70 kg sets off, with initial speed of 5 m(s^-1), down the line of greatest slope of an artificial ski-slope. The ski-slope is 80 metres long and is inclined at a constant angle of 20° to the horizontal. During the motion the skier is to be modeled as a...

Here is a question that I came across while doing my problem set questions: A boat experiences a resistive force that is proportional to v^2. If the maximum speed of a boat is V when one engine is at full throttle, what would be the maximum speed if two engines were used? I assume this...

I really need help with this! Homework Statement A 70-kg diver steps off a 10-m tower and drops from rest strait down into the water. If he comes to rest 5.0 m beneath the surface, determine the average resistive force exerted on him by the water.Homework Equations This is the only equation...

Homework Statement Consider a damped oscillator, with natural frequency \omega_{o} and damping constant B, both fixed, that is driven by force F(t) = F_{o}cos(\omegat). Verify that the average rate at which energy is lost to the resistive force is mB\omega^2A^2. Homework Equations x =...

1. The engine of an automobile requires 45hp to maintain a constant speed of 80 km/h a. What is the resistive force against the automobile? The answer given here is 1510.80N but don't know how they get it. b. If the resistive force is proportional to the velocity, what must the engine power be...

Homework Statement an object moves to the right with a constant speed v, the ovbject then enters a region where the resistive force is -bv2, find v(t) & x(t) Homework Equations The Attempt at a Solution Fx = ma = -bv2 v = (ma/-b).5 how do i get t in there

Homework Statement Ok so the problem is this: A car of a mass 960kg is free-wheeling down an incline (15 degrees to the horizontal) at a constant speed of 9.0 m s^-1 - Deduce that the average resistive force acting on the car is 2.4*10^3N Homework Equations F=ma I suppose, but it hasn't...

Homework Statement A bicyclist rides 5.7 km due east, while the resistive force from the air has a magnitude of 2.8 N and points due west. The rider then turns around and rides 4.6 km due west. The resistive force from the air on the return trip has a magnitude of 1.9 N and point due east...

Homework Statement At major league baseball games it is commonplace to flash on the scoreboard a speed for each pitch. This speed is determined with a radar gun aimed by an operator positioned behind home plate. The gun uses the Doppler shift of microwaves reflected from the baseball, as we...

Homework Statement A bicyclist rides 7.8 km due east, while the resistive force from the air has a magnitude of 2.4 N and points due west. The rider then turns around and rides 5.3 km due west. The resistive force from the air on the return trip has a magnitude of 4.5 N and point due east...

Good day, ladies and gentlemen. I am a long time board reader (since my high school days) but have not posted in these forums, till now. I initially registered with plans and hopes to enter a career in physics, now I am taking my first formal college level physics course, in the summer after my...

heheh...I need some help understanding something. If there was an object, such as a sphere, in water, gravity would be pushing it downwards, while a resistive force R = -bv would be pushing it upward (b as a constant). that would imply that the net Force Fy would be Fy = mg - bv = ma =...

Tell me if I am wrong or not, but you have a boat that weighs 1.70x10^8 kg and the engines are moving it with a forse of 7.40x10^5 Newtons. a.) I think that the magnitude of the resistive force exerted by the water is equal to the force the boat witch is 7.40x10^5, is this correct? b.) how do...

I have this question: A 10kg projectile is launched with an initial speed of 100m/s at an elevation of 35 degrees. The resistive force is R = -bv , where b =10kg/s. Determine the horizontal and vertical component coordinates of the projectile as functions of time. How do I do this?? I...

I'm looking for the formula for resistive force that involves "air density, speed of object, and cross-sectional area." I also need to know why it is an important factor in determinging air resistance, and include aerodynamics, drag coefficient, and terminal speed-how they relate to one...

Consider an object which the net force is a resistive force proportional to the square of its speed. For example: assume that the resistive force acting on a speed skater is F=-k*m*V^2, where k is a constant and m is the skater's mass. The skater crosses the finish line of a straight-line race...

Consider an object which the net force is a resistive force proportional to the square of its speed. For example: assume that the resistive force acting on a speed skater is F=-k*m*V^2, where k is a constant and m is the skater's mass. The skater crosses the finish line of a straight-line race...

Consider an object which the net force is a resistive force proportional to the square of its speed. For example: assume that the resistive force acting on a speed skater is f=-kmv^2, where k is a constant and m is the skater's mass. The skater corsses the finish line of a straight-line race...