# Acceleration question BASIC PHYSICS HELP

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" ?

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
Staff Emeritus
Homework Helper

Welcome to Physics Forums, AbovenBeyond and BrainGirl.

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

Hello,

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

Redbelly98
Staff Emeritus
Homework Helper

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.

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 :((

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
Staff Emeritus