Exercício de Dinamica (142)

Prévia do material em texto

PROPRIETARY MATERIAL. © 2013 The McGraw-Hill Companies, Inc. All rights reserved. No part of this Manual may be displayed, 
reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited 
distribution to teachers and educators permitted by McGraw-Hill for their individual course preparation. If you are a student using this Manual, 
you are using it without permission. 
153 
 
PROBLEM 11.105 
A homeowner uses a snowblower to clear his 
driveway. Knowing that the snow is discharged 
at an average angle of 40° with the horizontal, 
determine the initial velocity v0 of the snow. 
 
SOLUTION 
First note 0 0
0 0
( ) cos 40
( ) sin 40
x
y
v v
v v
= °
= °
 
Horizontal motion. (Uniform) 
 00 ( )xx v t= + 
At B: 0
0
14
14 ( cos40 ) or
cos 40Bv t t
v
= ° =
°
 
Vertical motion. (Uniformly accelerated motion) 
 2 2
0
1
0 ( ) ( 32.2 ft/s )
2yy v t gt g= + − = 
At B: 2
0
1
1.5 ( sin 40 )
2B Bv t gt= ° − 
Substituting for Bt 
 
2
0
0 0
14 1 14
1.5 ( sin 40 )
cos 40 2 cos 40
v g
v v
   
= ° −   ° °   
 
or 
21
2 2
0
(32.2)(196)/ cos 40
1.5 14 tan 40
v
°
=
− + °
 
or 0 22.9 ft/sv = 