Speed of ball bearing from a slingshot using sound delay

[junesmrithi]

Question: To find the speed of a ball bearing launched from a wrist rocket (sling-shot) you take aim at a 55 gallon steel drum exactly 78 meters from you. You hear the "clunk" of impact 0.7 seconds after you "let fly." If the speed of sound on that particular day is 330 m/s, how fast must the ball bearing be traveling?

 

[cristo]

This is clearly a homework question, so PF rules state that you must show your work before we can help you. What thoughts do you have on the question?

Also, in future, please post such questions in the homework forums.