Go Back   Physics Help Forum > High School and Pre-University Physics Help > Kinematics and Dynamics

Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

Reply
 
LinkBack Thread Tools Display Modes
Old Oct 26th 2008, 02:18 PM   #1
Member
 
Join Date: Sep 2008
Posts: 42
Simple Force problem

A lobster is in a tug of war against some smaller lobsters.
Its mass = 20.0 kg
The small lobsters drag the big lobster 1.55 m at 0.550 m/s.

Lobster is initally at rest. What is the magnitude of the force applied to the lobster? Ignore friction and water.
Morgan82 is offline   Reply With Quote
Old Oct 28th 2008, 09:11 PM   #2
Senior Member
 
Join Date: Apr 2008
Location: HK
Posts: 886
Originally Posted by Morgan82 View Post
A lobster is in a tug of war against some smaller lobsters.
Its mass = 20.0 kg
The small lobsters drag the big lobster 1.55 m at 0.550 m/s.

Lobster is initally at rest. What is the magnitude of the force applied to the lobster? Ignore friction and water.
use the equation of motion
$\displaystyle v^2-u^2=2as$
u is the initial velocity which would be zero.
s is the displacement , a is the acceleration

You find the acceleration and then you use
F = ma
to find the force.
werehk is offline   Reply With Quote
Old Oct 29th 2008, 02:14 AM   #3
Junior Member
 
Join Date: Apr 2008
Posts: 14
Originally Posted by Morgan82 View Post
A lobster is in a tug of war against some smaller lobsters.
Its mass = 20.0 kg
The small lobsters drag the big lobster 1.55 m at 0.550 m/s.

Lobster is initally at rest. What is the magnitude of the force applied to the lobster? Ignore friction and water.
Lets assume constant force and hence acceleration, that the average speed over the $\displaystyle 1.55 $m is $\displaystyle 0.550 $m/s, and the initial speed is $\displaystyle 0$, and the initial position is $\displaystyle s=0$. Also assume movement is in the positive direction so our speed and velocity are the same as long as we are moving to the right.

Then the equation of motions give:

$\displaystyle
v=at
$

$\displaystyle
s=\frac{at^2}{2}
$

and if $\displaystyle t_1$ is the time over which the displacement takes place, the average speed (velocity) is:

$\displaystyle
\bar{v}=0.55=\frac{at_1}{2}
$

and

$\displaystyle
s_1=1.55=\frac{at_1^2}{2}
$

Now solve these for $\displaystyle t_1$ and a, and then use $\displaystyle F=ma$ to find the force.

CB

Last edited by CaptainBlack; Oct 29th 2008 at 02:17 AM.
CaptainBlack is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Kinematics and Dynamics

Tags
force, problem, simple


« Net Torque | Force! »

Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
simple force vector problem furor celtica Kinematics and Dynamics 2 Jan 12th 2012 08:32 AM
Simple Momentum (Force V Time graph) brun2008 Kinematics and Dynamics 1 Sep 14th 2011 04:55 AM
simple question about normal force hapflir Kinematics and Dynamics 1 Apr 5th 2009 06:32 PM
a simple buoyany force question... harbong Kinematics and Dynamics 0 Nov 20th 2008 08:02 AM
Need help with a Simple Force Diagram Question trent19 Kinematics and Dynamics 0 Aug 28th 2008 03:17 AM


Facebook Twitter Google+ RSS Feed