Welcome :: Homework Help and Answers :: Mathskey.com

Recent Visits

    
Welcome to Mathskey.com Question & Answers Community. Ask any math/science homework question and receive answers from other members of the community.

13,435 questions

17,804 answers

1,438 comments

777,244 users

Physics help?

0 votes
A girl throws a set of keys straight upward to her sister, who is in a window 3.60 m above her hand. The sister catches the keys in her outstretched hand 1.50 s later. 
a.​With what initial velocity were the keys thrown? 
b.​What was the velocity of the keys just before they were caught? 
c.​Were the keys traveling upward or downward just before they were caught?
 
asked Sep 15, 2014 in PHYSICS by heather Apprentice

3 Answers

0 votes

(a)

From the given data we can understand that the ball was thrown vertically upwards ,

So for Verticall upword moving bodies have a sufficient intial velocity (u)

We use the relation s = ut +½ at²

But for vertically upward moving objects acceleration due to gravity is negitive a= -g

h = ut - ½ gt²    

Where h is height , t is time , u is intial velocity

3.6 = u(1.50) - ½ (9.8)(1.50)²

u(1.50) = 3.6 +11.025

u(1.50) = 14.625

u = 9.75

 Initial velocity of keys when thrown u = 9.75 m/s (Upward)

answered Sep 15, 2014 by friend Mentor
0 votes

(b)

To find the velocity of keys just before it was caught , we use the relation v =u+at

Where u is intial velocity = 9.75 m/s,

a is acceleration due to gravity nagitive in this case ( a = -g ) & t =1.5 s

v = u -gt

v = 9.75 - (9.8)(1.5)

v = 9.75 - 14.7

v =  - 4.95 m/s

velocity of the keys just before it was caught is v =  4.95 m/s (downwards)

answered Sep 15, 2014 by friend Mentor
edited Sep 15, 2014 by bradely
0 votes

(c)

From (b) we clearly notice that the velocity of key just before it was caught is v =  - 4.95 m/s

Here the negitive sign indicate that the sister caught the keys in way back , 

Means it reaches its maximum height and in the return she caught the keys

So the keys traveling downward just before it was caught

answered Sep 15, 2014 by friend Mentor

Related questions

asked Jun 29, 2017 in PHYSICS by anonymous
asked Jan 26, 2016 in PHYSICS by anonymous
asked Jan 26, 2016 in PHYSICS by anonymous
asked Jan 26, 2016 in PHYSICS by anonymous
asked Jan 26, 2016 in PHYSICS by anonymous
asked Jan 26, 2016 in PHYSICS by anonymous
asked Nov 29, 2015 in PHYSICS by anonymous
...