A curling rink is approximately 35 m long from button to button. Mr. Grover releases a rock and 20. seconds later it stops on the far button. What was the initial velocity of the stone? What deceleration did it undergo?

  • Initial velocity = ?
  • Final velocity = 0 m/s
  • Time = 20 seconds
  • Acceleration = ?
  • Distance = 35 m

Did I forget anything because I can't use any of the formulas I learned if I'm missing two things.

Formulas \begin{align} v_{f} &= v_{i} + at\\ v_{f}^2 &= v_{i}^2 + 2 ad\\ d &= v_{i} t + \frac12 at^2\\ a &= \frac{v_{f} - v_{i}}{t}\\ \end{align}


closed as off-topic by John Rennie, Ali, Qmechanic Oct 17 '14 at 14:27

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – John Rennie, Ali, Qmechanic
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ You're forgetting a couple average velocity equations. Find the average velocity of the stone over the time interval, and then use that and the final velocity to find an initial velocity $\endgroup$ – Sean Oct 17 '14 at 1:22

Use $d=v_i t +\frac{1}{2}a t^2$ and then substitute from the first equation that $v_i=-a t$. You get $$d= -at^2+\frac{1}{2}at^2=-\frac{1}{2}at^2$$ from which you can infer $$ a=-\frac{2d}{t^2}$$ Once you have the acceleration you get the initial velocity from $v_i=-a t$.


Not the answer you're looking for? Browse other questions tagged or ask your own question.