Home » Ask & Discuss » Physics. » Mechanics « Back to Discussion

Mechanics

Scorching goIITian

Joined:	3 May 2008
Post:	288

13 Aug 2009 00:37:38 IST

0 People liked this

324

kinematics ques....

Kinematics , NewtonsLawsCirMotion , Work Power Energy collisions , Rotation , Gravitation , Simple Harmonic Motion , Fluid Mechanics , Materials Wave Sound , Super Position , units dimensions , com momentum , shm , wave sound

a thief in a stolen car crashes through a police checkpost at his top speed of 90 km/h...a mototrcycle cop reactng aftr 2 sec acclerates frm rest at 5 m/sec^2..his top speed being 108km/hr..find the maxm seperation between police nd thuief....

Share this article on:

Comments (1)

Bhimsen Padalkar

Scorching goIITian

Joined: 29 Oct 2008

Posts: 298

13 Aug 2009 10:16:46 IST

Like 2 people liked this

After 2 sec., dist travelled by theif = 2 x 25 = 50 m (90km/h = 25m/s)

Taking this instant (when cop starts chasing) as t = 0, at any instant t, the dist of theif from checkpost = 25t + 50

Dist. of cop from checkpost = 1/2 at² = 5/2 t²

Let x be the separation b/w them which is given as function of time as x = (25t + 50) - 5/2 t²

When separation is max. dx / dt = 0

i.e. 25 - 5t = 0 ==> t=5

Therefore, x = 175 - 62.5 = 112.5 m

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team