• Support PF! Buy your school textbooks, materials and every day products Here!

2 questions

  • Thread starter brad sue
  • Start date
281
0
Hey ,

I

I need to verify my work about this problem:
Two small objects A and B are suspended from the ends of a rope thrown over a pulley. Object A is at 1.2 m above B when the system is at rest. Object A descends with a downward acceleration of 0.3m/s2 and because of the rope, B accelerates upward at the same rate. How much time elapses before the objects bump each other?

I found t=2seconds

II


A softball picher pitches a ball at 65 mph.
The distance from the pitcher's mound to home plate is 43ft, but the pitcher realeases the ball about 41 ft from the home plate.
a- How long does it takes for the ball to reach home plate? (I found it t=.43s)
b-A Good pitcher can make the ball curve left about 6 inches over the pitch distance. If this is due to a constant acceleration, what is its magnitude and which direction does it act?

For this second question I do not know how to do it
need some suggestions
.

Thank you
brad
 

Answers and Replies

Fermat
Homework Helper
872
1
The first two answers are correct.

For IIb, the ball curves to the left, so the acceln must be in the same dirn, no!!

You are given the distance moved - 6 inches - and the time taken - the time for the pitcher to reach the home plate.
Use the standard eqns of motions now.
 
281
0
question (bis)

Sorry, but I still dont get perhaps I have difficulty to represent the scene . I do not know baseball well!!
but I continue searching!
 
Fermat
Homework Helper
872
1
Forget the baseball.

Consider the question as:

A particle, starting from rest and moving under a constant acceleration, moves a distance of 6 inches in 0.43 sec. What is its acceleration ?

When the baseball is thrown, it has an intial velocity of 65 mph, but that is in the forward direction, from mound to plate. It won't have any (initial) velocity in the sideways direction, just a small amount of acceleration.
 
Last edited:
281
0
Fermat said:
Forget the baseball.

Consider the question as:

A particle, starting from rest and moving under a constant acceleration, moves a distance of 6 inches in 0.43 sec. What is its acceleration ?

When the baseball is thrown, it has an intial velocity of 65 mph, but that is in the forward direction, from mound to plate. It won't have any (initial) velocity in the sideways direction, just a small amount of acceleration.
ok! Thanks I see what to do now!!
 

Related Threads for: 2 questions

  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
3
Views
906
  • Last Post
Replies
7
Views
2K
Top