Go Back   Physics Help Forum > College/University Physics Help > Advanced Mechanics

Advanced Mechanics Advanced Mechanics Physics Help Forum

Like Tree1Likes
  • 1 Post By sagnaq997
Reply
 
LinkBack Thread Tools Display Modes
Old Feb 26th 2017, 11:50 AM   #1
Junior Member
 
Join Date: Feb 2017
Posts: 2
Ball on inclined plan frictionless



Hi there, I need help for this question.

I assumed d=20
and m=2

since i cannot use conservation of energy i couldnt solve it. I found the acceleration which is mgsin30=4.9 i put it on the formula v (final velocity)=u(initial)+at^2

v=4.9t^2

when i put this on the formula s=(u+v/2)*t

I got v=14 is that correct ?

I could find h

and i need help for d and e ( i did not understand since I'm not a native english speaker)
sagnaq997 is offline   Reply With Quote
Old Feb 26th 2017, 04:55 PM   #2
Forum Admin
 
topsquark's Avatar
 
Join Date: Apr 2008
Location: On the dance floor, baby!
Posts: 2,070
Originally Posted by sagnaq997 View Post


Hi there, I need help for this question.

I assumed d=20
and m=2

since i cannot use conservation of energy i couldnt solve it. I found the acceleration which is mgsin30=4.9 i put it on the formula v (final velocity)=u(initial)+at^2

v=4.9t^2

when i put this on the formula s=(u+v/2)*t

I got v=14 is that correct ?

I could find h

and i need help for d and e ( i did not understand since I'm not a native english speaker)
m = 2 kg, d = 20 m

(I presume you made a force diagram.)

b) Use the definition of sine: $\displaystyle sin(30) = \frac{h}{d}$. So you can find h from here.

c) Your tactic of using Newton's 2nd to find the acceleration is good. But it's $\displaystyle F_{down} = ma = m \cdot (-g~cos(30) )$. You have an extra m in your equation. Now you can finish off with your equation to find v.

d) The ball is now initially traveling up the incline with a new acceleration (deceleration, really) with an initial speed you found in c).

e) In the first part h is the height where the ball started. You need to use the speed in (d) as the initial speed.

Is that detailed enough or do you need more help in understanding what d) and e) are asking for?

-Dan
__________________
I'm a "something shiny" kind of...Oh look! Something shiny!

See the forum rules here.
topsquark is offline   Reply With Quote
Old Feb 27th 2017, 12:51 AM   #3
Junior Member
 
Join Date: Feb 2017
Posts: 2
Originally Posted by topsquark View Post
m = 2 kg, d = 20 m

(I presume you made a force diagram.)

b) Use the definition of sine: $\displaystyle sin(30) = \frac{h}{d}$. So you can find h from here.

c) Your tactic of using Newton's 2nd to find the acceleration is good. But it's $\displaystyle F_{down} = ma = m \cdot (-g~cos(30) )$. You have an extra m in your equation. Now you can finish off with your equation to find v.

d) The ball is now initially traveling up the incline with a new acceleration (deceleration, really) with an initial speed you found in c).

e) In the first part h is the height where the ball started. You need to use the speed in (d) as the initial speed.

Is that detailed enough or do you need more help in understanding what d) and e) are asking for?

-Dan
hi I did not get the c where does cos come from isn't it sin ?
topsquark likes this.
sagnaq997 is offline   Reply With Quote
Old Feb 27th 2017, 01:37 PM   #4
Forum Admin
 
topsquark's Avatar
 
Join Date: Apr 2008
Location: On the dance floor, baby!
Posts: 2,070
Originally Posted by sagnaq997 View Post
hi I did not get the c where does cos come from isn't it sin ?
Yes it should be mg sin(30). Thanks for the catch.

-Dan
__________________
I'm a "something shiny" kind of...Oh look! Something shiny!

See the forum rules here.
topsquark is offline   Reply With Quote
Reply

  Physics Help Forum > College/University Physics Help > Advanced Mechanics

Tags
ball, frictionless, inclined, plan



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Rotating and translation on a frictionless surface hadsox Advanced Mechanics 4 Jan 12th 2017 01:43 PM
Particle at the bottom of a frictionless slope bilbo Advanced Mechanics 11 Jun 1st 2013 01:41 AM
Ball drops and ball tthrow at same time.. LittleWing Kinematics and Dynamics 3 Mar 7th 2011 11:03 AM
a girl and a sled on frictionless ice oblixps Kinematics and Dynamics 1 Sep 29th 2009 02:01 AM
speed down a frictionless hill chaoticphysics Kinematics and Dynamics 1 Mar 31st 2009 10:06 PM


Facebook Twitter Google+ RSS Feed