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

Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

Like Tree1Likes
  • 1 Post By HallsofIvy
LinkBack Thread Tools Display Modes
Old Apr 16th 2019, 05:25 AM   #1
Junior Member
Join Date: Apr 2019
Posts: 15
Relative velocity and accel. question? Can't figure out what velocity


The question in question is number 2.

The velocity must be 2, right? How would I go about getting a different number?

The time for the phone to get to the edge is 10 seconds, so that means they have to get there in 10 seconds, too. If they were to start immediately after they miss then they only need to be going the same velocity, right?

Where am I going wrong and how to get the right number?

Thank you for any replies

EdIt: i got it lol i used d=0.5at^2 my bad thanks yall lolol

Last edited by astupidummydumstupid; Apr 16th 2019 at 05:37 AM.
astupidummydumstupid is offline   Reply With Quote
Old Apr 16th 2019, 08:52 AM   #2
Senior Member
Join Date: Aug 2010
Posts: 398
Problem 2 does not ask anything about velocity, it asks for acceleration. The phone passes you at 2 m/s. After "t" seconds, it will have gone 2t meters. If you start after it with constant acceleration, a, in "t" seconds, you will have gone $(a/2)t^2$ meters. You will catch up to the phone when those two distances are the same, $(a/2)t^2= 2t$. That quadratic equation has two solutions. One of them is t= 0 when the phone first passed you. The other solution is when you catch up to it. That will, of course, depend on a. Then you need to put that value of t into 2t to find the distance the phone goes before you catch it. That will, again, depend on a. What must a be so that the distance is less than 20 m?
topsquark likes this.

Last edited by HallsofIvy; Apr 16th 2019 at 09:35 AM.
HallsofIvy is offline   Reply With Quote

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

accel, figure, question, relative, velocity

Thread Tools
Display Modes

Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Question involving a cannon, cannonball, and relative velocity pereeia Kinematics and Dynamics 3 Apr 22nd 2017 04:11 PM
Relative velocity qns Miguelogy Kinematics and Dynamics 1 Aug 25th 2013 08:05 AM
velocity velocity of the plane relative to the ground Taurus3 Kinematics and Dynamics 3 Jan 13th 2011 04:49 AM
Relative velocity physics123456 Kinematics and Dynamics 2 Oct 5th 2009 06:50 AM
Relative Velocity Fracman Kinematics and Dynamics 1 Oct 28th 2008 09:15 PM

Facebook Twitter Google+ RSS Feed