Tagged Questions
5
votes
1answer
61 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 ...
0
votes
2answers
74 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 ...
0
votes
3answers
91 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 ...
2
votes
0answers
91 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, ...
7
votes
4answers
471 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 ...
5
votes
2answers
239 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 ...
2
votes
1answer
112 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 ...
3
votes
2answers
166 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 ...
1
vote
2answers
113 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 $D$. ...
-1
votes
2answers
334 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) ...
7
votes
1answer
391 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 ...
0
votes
1answer
127 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 ...
1
vote
0answers
73 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 ...
0
votes
2answers
104 views
Is air drag equation in term of momentum still valid?
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?
$$m{\bf v}=mv_g-b{\bf r}.$$
4
votes
2answers
104 views
What was the muzzle velocity of a home made gun launch strait in the air if air time was 8.2sec?
I built a potato gun and wanted to calculate the muzzle velocity. I remember from physics that I could run the numbers by calculating time from launch until landing. After pointing strait into the air ...
0
votes
0answers
65 views
I'm having trouble understanding the dimensions of this falling body problem
I'm working with this:
A 50 kg mass is shot from a cannon straight up with an initial
velocity of 10m/s off a bridge that is 100 meters above the ground.
If air resistance is given by 5v ...
1
vote
1answer
125 views
How much runway does the space shuttle need to land?
A textbook question proposes the following scenario:
NASA needs to plan emergency landing sites for the Space Shuttle (RIP). There are a number of things to consider. The shuttle touches down no ...
1
vote
2answers
116 views
Kinetic Energy of Stone
If a stone is launched upward, of which is subject to gravity and air resistance, which of the following will have a greater kinetic energy? The stone at a point on its way up, or the stone at the ...
2
votes
2answers
169 views
Parabolic motion and air drag
Are this equations correct, in order to calculate the parabolic motion of an arrow with the computation of the drag with the air?
$$
\begin{cases}
x(t)=\left(v_0-\frac{1/2C_DA\rho ...
1
vote
1answer
410 views
Friction due to air drag at high speeds
I am trying to set up this problem, but I am not sure how to go about doing so. (From University Physics, Young & Freedman):
You throw a baseball straight up. The drag force is proportional to
...
-1
votes
1answer
247 views
How does Baumgartner slow his velocity so that the parachute can open up?
How does Baumgartner slow his velocity so that the parachute can open up?
What is Baumgartner's speed just before his parachute opens?
What causes his speed to slow down just before the chute opens?
...
26
votes
6answers
22k views
Could someone jump from the international space station and live?
Felix Baumgartner just completed his breathtaking free-fall skydiving jump from $120,000\,\text{feet} = 39\,\text{km}$ above the Earth, breaking the speed of sound during the process.
I was wondering ...
4
votes
4answers
2k views
How Felix Baumgartner has reached the speed of sound quickly
I have watched Felix Baumgartner freefall; but I wonder how Felix has reached the speed of sound quickly, in a matter of some seconds, then we had no idea of its speed?
Any explanation please.
0
votes
1answer
89 views
Time of a ball going up and down with air resistance
A ball is shot directly upward, and then it comes back to the place where it was shot. Suppose we have air resistance. Suppose $t_1$ is the time period from the moment that the ball was shot to the ...
3
votes
2answers
181 views
Does air resistance ever slow a particle down to zero velocity?
If a particle moves in a place with air resistance (but no other forces), will it ever reach a zero velocity in finite time? The air resistance is proportional to some power of velocity - $v^\alpha$, ...
2
votes
3answers
516 views
Why would a fat skydiver fall first in free fall?
I was having one of those obnoxious conversations with a friend where he was arguing that a fat skydiver would reach the ground faster than a skinny skydiver. To me it seemed as obvious that the world ...
0
votes
1answer
156 views
How can the Air friction force be applied to an object?
Suppose we have an object and we throw it straight upward in the air. How do we apply the Air friction force to this object while moving upwards and after that downwards? Sorry if it's easy because ...
1
vote
3answers
426 views
Is it possible to find out the distance traveled by a car if the force applied on it is given?
Say you have car which produces $F$ amount of force which is transferred to the wheels directly.
Now assuming that there is air friction which is causing a retarding force proportional to the ...
1
vote
2answers
1k views
Equations for an object moving linearly but with air resistance taken into account?
I know (from Kinematics) that for an object moving linearly with an acceleration and without air resistance the following equations can be used to determine v(velocity) or x(position of the object) at ...
0
votes
2answers
223 views
Bicycle Wheel Drag in Slipstream
I was recently driving behind a car that had a bicycle mounted on a carrier over the rear bumper.
The bicycle wheels were not bound so they were rotating in the slip-stream of the car.
I wonder, the ...
3
votes
2answers
213 views
At what g is terminal velocity not terminal?
How weak would gravity need to be in order for a human to reliably survive the terminal velocity of falling through air?
(Context: watching scifi on a space station with a variety of artificial ...
3
votes
3answers
393 views
Does wind speed things up or accelerate things?
This question may seem odd, but I can't think of anything better. So I'll go straight to the point.
Let's say there's a projectile in air going east, shot at a certain angle, with a certain speed. ...
0
votes
2answers
2k views
Why does a parachute decrease terminal velocity?
Terminal Velocity depends on two things- surface area and speed. These are inversely proportionate.
If both these variables affect terminal velocity, why do parachutes slow you down? Initially you ...
2
votes
2answers
245 views
Does a ski racer with a larger mass have an advantage?
Does a ski racer with a greater mass have an advantage over a racer with a lesser mass?
If mass of one racer is 54 kg and the mass of a more slender racer is 44 kg I know the speed at which they ...
3
votes
1answer
1k views
How to modify the bullet trajectory based on the ballistic coefficient?
I am new to the physics surrounding bullet trajectory and how it is calculated. I am a software developer and I am working on a ballistics calculator for rifles. I am using wiki for the trajectory ...
2
votes
3answers
96 views
How can I modify the bullet trajectory based on the ballistic coefficient? [duplicate]
Possible Duplicate:
How to modify the bullet trajectory based on the ballistic coefficient?
I am new to the physics surrounding bullet trajectory and how it is calculated. I am a software ...
2
votes
3answers
830 views
What is terminal velocity?
What is terminal velocity? I've heard the term especially when the Discovery Channel is covering something about sky diving. Also, it is commonly known that HALO (Hi-Altitude, Lo-Opening) infantry ...
