Acceleration question BASIC PHYSICS HELP

[AbovenBeyond]

Acceleration question BASIC PHYSICS HELP :(

Question1: A ball rolls with an acceleration of 20.5m/s^2. If it stops after 7s, what was its initial speed ? (Answer 3.5 m/s )

Question2: A wheelchair marathoner has a speed of 5m/s after rolling down a small hill in 1.5 s. If the wheelchair underwent a constant acceleration of 3m/s^2 during the descent , what was the marathoners speed at the top of the hill ? (Answer: 0.5m/s)

Question3:

What does it mean when it says in a problem: "at a 45* angle from due East and from due North" ?

Please, please help me figure those questions out with explanation.
Very much appreciate your help.


Thank you in advance

 

[BrainGirl]

Hi,

When I took physics for the first time in high school many years ago I purchased The Cartoon Guide to Physics by Larry Gonick. I don't think I would have done as well as I did without it. The cartoons were amusing and helped me to visualize the problems which made solving them that much easier!

I don't want to take away from your experience of solving the problems for yourself but I will suggest that they may require the use of multiple formulae:) If you need them, you can get them here: http://www.physics247.com/physics-tutorial/acceleration.shtml

Hope this helps!

 

[Redbelly98]

Welcome to Physics Forums, AbovenBeyond and BrainGirl.

AbovenBeyond, what is the definition of acceleration? What equation is given along with that definition?

 

[AbovenBeyond]

Hello,

Acceleration = (change in velocity) /( change in time)
20.5m/s^2= (change in Velocity) / 7s
=143.5m/s

 

[Redbelly98]

Question1: A ball rolls with an acceleration of 20.5m/s^2. If it stops after 7s, what was its initial speed ? (Answer 3.5 m/s )

Hello,

Acceleration = (change in velocity) /( change in time)
20.5m/s^2= (change in Velocity) / 7s
=143.5m/s

You're correct, the answer 3.5 m/s is wrong.

 

[AbovenBeyond]

Can someone please explain to me how to do this question, even better solve it and explain the steps.. I find it quite difficult.
Question2: A wheelchair marathoner has a speed of 5m/s after rolling down a small hill in 1.5 s. If the wheelchair underwent a constant acceleration of 3m/s^2 during the descent , what was the marathoners speed at the top of the hill ? (Answer: 0.5m/s)

HELP :((

 

[lordZeR0]

Did you draw a diagram(label what happens where and when , velocityInital= ? , velocityFinal=? , Acceleration=? StartPosition =? , EndPosition=? That always helps me in addition to putting closely related equations next to the drawing.

 

[Redbelly98]

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