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 Nov 19th 2015, 06:43 PM   #1
Junior Member
 
Join Date: Nov 2015
Posts: 2
Kinematics help!?

A student is late to the city bus. The bus starts from rest and begins to leave the stop at an acceleration of 1m/sē. The student turns the corner and sees the bus leaving 20m ahead of them. What is the smallest constant velocity with which the student will need to run to JUST catch the bus before it accelerates away too fast to intercept. (the bus never stops accelerating, the student just needs to intercept the bus.)
nolanbradshaw01 is offline   Reply With Quote
Old Nov 20th 2015, 04:38 AM   #2
Physics Team
 
ChipB's Avatar
 
Join Date: Jun 2010
Location: Morristown, NJ USA
Posts: 2,347
You can set up two equations in two unknowns, then solve for those unknowns. First you have the fact that the student and bus must be at the same place at the same time. Let's call the student's velocity 'v' and the time it takes to catch the bus 't' - the equation that has them at the same place at the same time is:

vt = 20 + (1/2)at^2

The second condition is that the student just barely catch the bus before it accelerates away - this is equivalent to saying that at the moment the student reaches the bus the velocity of the student = the velocity of the bus:

v = at

You know the value for 'a', so now you can solve for 'v' and 't'.
ChipB is offline   Reply With Quote
Reply

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

Tags
help please, kinematics



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Kinematics amit6234623 Kinematics and Dynamics 1 Oct 8th 2015 06:13 AM
Kinematics Aladdin Kinematics and Dynamics 8 Apr 3rd 2011 11:08 AM
Kinematics hah842 Kinematics and Dynamics 2 Sep 24th 2010 08:31 AM
Kinematics Help Fazil Kinematics and Dynamics 5 Mar 20th 2009 11:47 AM
kinematics, please help, devanlevin Kinematics and Dynamics 0 Nov 17th 2008 09:25 AM


Facebook Twitter Google+ RSS Feed