Tagged Questions

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Small Animal Terminal Velocity

I recently saw a cat fall probably 100 feet like in this video Cat Falls. It seemed as if the cat reached terminal velocity by the time it hit. Does this mean that cats (and other small animals) could ...
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What is the maximum range of a bullet flying through the sky? [closed]

How far would my bullet fly with the following characteristics? 1.2km/second initial velocity 45 degree angle into the sky 'Normal' atmospheric conditions No wind Typical high-powered rifles have ...
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What is the speed of a thrown ball [closed]

I would like to know how much speed is loss when a baseball is pitched. When a pitcher hurls the ball, it must lose speed before the catcher catches it because of the air resistance. So, if the ...
206 views

How fast would a truck have to go to pull a pedestrian onto the road? [on hold]

Let's suppose a pedestrian P is walking or standing next to a highway. Suppose a truck T will drive by the said pedestrian at speed V leaving distance L between the two. Assuming L is a reasonably ...
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Ice throw from industrial wind turbine

I was watching a documentary where the residents didn't want to have a wind turbine erected nearby. One of the comments from the company was that an ice throw would have very little importance since ...
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Motorbike with parachute vs normal skydive

Had a strange discussion in the coffeeroom today. The background was a story about a guy that took his motorcycle to transport himself to the airstrip to do a skydive. Since there is no place to put ...
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Is speed squared constant?

q. A heavy particle is projected at speed $U$ at an angle $\alpha$ to the horizontal. The particle is subject to air resistance which is experimentally found to vary proportionally to the square ...
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3D ballistic trajectory with quadratic drag. Calculating position and velocity at time $t$

A particle starts at the origin and has an initial velocity represented by a 3D vector. The particle experiences gravity and air resistance with quadratic drag (based on velocity^2). What I've been ...
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Bernoulli's principle on a curve ball

I've seen a few excellent answers here on the Magnus force, which explains why balls with a spin will curve. However, my intuition is still telling me that the Bernoulli's principle would push it the ...
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Obtain rate as a function of position for a force $F=-b\left( \frac{\partial x}{\partial t} \right)^{2}$

I have trouble getting the speed as a function of position for a force of the form: $$F=-b\left( \frac{\partial x}{\partial t} \right)^{2}$$ I had thought to use Newton's second law, so: ...
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How to plot $(x,y)$ coordinate of projectile motion (with air-resistance)? [closed]

I am trying to plot a graph to show the difference in projectile motion when it has air-resistance and when it doesn't have air-resistance. I set the mass, $v_0$ and $\theta$ as constant I can plot ...
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Modeling with First Order Equations [closed]

A ball with mass 015kg is thrown upward with initial velocity 20m/s from the roof of a building 30m high. There is air resistance of magnitude v^2/1325 directed opposite to the velocity , where the ...
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Is there a better approximation of drag (other than quadratic drag)?

This is a student inquiry sparked by sheer curiosity. Wikipedia states the drag equation, $F = 1/2v^2pC_dA_c$. (p = mass density of fluid/gas, v = velocity, c_d = drag coefficient, a_c = cross ...
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Terminal Velocity Question [closed]

Question: A ball of mass m is thrown vertically upward with initial velocity $v_0$. Air resistance is proportional to the square of the velocity. If the terminal velocity of the ball is $v_t$, show ...
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Drag Force per point in the body

Let us consider the common equation for drag force for any body. $F_D = \frac{1}{2}\rho v^2C_dA$ Here the A is the representative area which is the so called area of cross section of the body for ...
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Drag/air-resistance impulse

I'm simulating snowfall in a discrete-time physics engine, using this formula for the drag force on a snowflake: $F_d=CAv^2$ (where $A$ is the flake's cross-sectional area and $C$ is a catch-all ...
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Resistive force proportional to velocity

Find the displacement and velocity of horizontal motion in a medium in which the retarding force is proportional to the velocity. I kind of understand how to do this problem. We know that the ...
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Conservation of momentum when friction is present

Conservation of momentum applies when net force is zero. Suppose that there is a system of a canon and a canonball. Total momentum of the system is zero before canonball is fired. Now canonball is ...
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$\gamma$ in Newton's Second Law of Motion in Differential Form

I am teaching myself Differential Equations from a website. In the website I am up to Direction Fields and an example of a differential equation is Newton's Second Law of Motion. It is written on the ...
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Air resistance of a general shape object

I'm trying to code a simple physics simulator in C++ but I'm stuck on the air resistance issue. Surfing the Internet I only find a drag coefficient for very basical area shapes when the air is ...
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Does the time to reach the highest point $P$ equal the time to reach the ground from $P$ in a trajectory, taking drag into account?

Assume a very simplified model without Corolis effect, the falloff of the local gravitational field and the like. My answer is no. It is sufficient to look at the vertical velocity of the projectile, ...
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What would a person experience in a free-falling elevator in a shaft long enough to reach terminal velocity?

Assume we had an elevator shaft long enough for a free-falling elevator to reach terminal velocity. As I understand it, when the elevator begins to fall a person inside would experiences ...
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Finding the drag force (Air resistance force) for accelerated ball?

As you know if I want to find the force for an accelerated object I will use the law $F_o=ma$ so I can get the affecting force of it. But there is another force affecting against the object. It's the ...
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How do I calculate the distance a ship will take to stop?

I am a River Pilot and drive ships for a living. These ships are very large and range up to 160,000 Metric Tons. I am trying to figure out how to calculate the distance to stopping. I have a basic ...
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Calculating Mass for a Reduced Trajectory while Keeping Projectile Force Constant

Apologies if this is not a research-specific question, but applied mechanics. A firefighter has to pass a test in which he is to throw a medicine ball a certain distance. The ball is thrown at a 45 ...
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Is there another way to calculate the work done by air resistance?

A ball of mass $0.37\text{ kg}$ is thrown upward along the vertical with a initial speed of $14\text{ m/s}$, and reaches a maximum height of $8.4\text{ m}$. a) What is the work done by air ...
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Are the forces I'm using correct? (ball in air) [closed]

I have been working on a program which should simulate all the forces on a spherical object. Right now those are balls, but they can easily be changed to something else. These are the formulas I use ...
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If a penny is dropped from the Empire State Building, then its speed, without taking air resistance into consideration, is $\sqrt{\left(32\frac{\textrm{ft}}{\textrm{s}^2}\right)(1454\textrm{ ... 4answers 5k views Terminal velocity of all falling objects is same? Ideally 2 objects of different mass and weight will hit the floor at same time because they face same gravitational pull and accelerate. Will the terminal velocity of both objects be same also? and ... 1answer 886 views In tennis, why does topspin serve bounce higher than flat serve? When receiving servers (while playing tennis), I've noticed that the tennis ball seems to bounce up higher on me when the server uses a topspin serve than when the server hits a flat serve. Why is ... 2answers 171 views How to calculate time for ball to reach plane while considering mass, gravity and wind resistance? The scenario that I'm having is such that a ball of radius$15mm$is thrown from a location point$\vec{p}=(2, 5, 2)$in a direction of$\vec{d}=(3, 0, 4)$. The initial velocity is$30m/s$. There were ... 3answers 306 views Parachute in vacuum Consider that the earth is vacuum. Consider a person of weight 100 kg is falling from sky with an parachute . He is free falling at height of 3000 m. When will he reach the ground? What would happen ... 0answers 224 views Why did increasing the Ackermann geometry in my race car make it faster in corners? Ackermann geometry is used to account for the different radius arcs that the front tires follow when the steering wheel is turned from center. It's often expressed as a percentage: e.g. 25% Ackermann, ... 4answers 2k views What causes a soccer ball to follow a curved path? Soccer players kick the ball in a linear kick, though you find it to turn sideways, not even in one direction. Just mid air it changes that curve's direction. Any physical explanation? Maybe this ... 2answers 2k views Explanation that air drag is proportional to speed or square speed? A falling object with no initial velocity with mass$m$is influenced by a gravitational force$g$and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ... 1answer 377 views Skiing downhill The other day on skiing holiday we've been arguing about whether an adult has weight advantage over a child when skiing downhill. I was claiming that gravity is a constant regardless of object's ... 2answers 733 views Finding optimal angle for projectile, taking into account linear (Stokes) drag If you throw a projectile from the ground at a certain angle, it's not hard to see that, assuming we're in a vacuum, throwing it at 45º from the ground will always make it go farthest before it hits ... 2answers 194 views Estimating atmospheric friction by measuring the change in velocity of a ball thrown straight upwards Imagine I throw a ball straight upwards with some velocity$v_1$, and filming the ball with a camera, I can estimate a velocity$v_2$(along the same vector) after the ball has moved a distance$D$. ... 2answers 2k views Work done by the air resistance [closed] A ball of mass 0.37 kg is thrown upward along the vertical with a initial speed of 14 m / s, and reaches a maximum height of 8.4 m. a) What is the work done by air resistance on the ball? b) ... 1answer 714 views Equation for the trajectory of a frisbee? I'm the lead programmer on a FIRST robotics team, and this year's competition is about throwing Frisbees. I was wondering if there was some sort of "grand unified equation" for Frisbee trajectory that ... 1answer 343 views Is resistance to motion directly proportional to the speed of a moving object? Power is known to be equal to the force x velocity (P=FV). Im solving a question that states the following : Car with engine working at 32 kW, mass of 1 tonne, travels at a constant speed of 40m/s ... 0answers 83 views Integration question from book “e: The Story of a Number” by Eli Maor [closed] In the book 'e: The Story of a Number', a derivation of a parachutist problem is given on pg. 109-110. A parachutist jumps from a plane and at$t=0\$ opens his chute. At what speed will he reach the ...
This is the known equation of air drag: $$m{\bf a}=mg-\mathcal D=mg-b{\bf v}.$$ Considering this, is air drag equation in term of momentum still valid? $$m{\bf v}=mv_g-b{\bf r}.$$