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Falling objects drop with an average acceleration of 9.8m/sec/sec. If an object falls from a tall building, how long will it take before it reaches a speed of 7m/s?

Thank you Jonas
15 September 2016
Leonora speed is measured in meters per second (m/s) not m/s/s which is an acceleration. Why do you feel the need to write out Jonas' correct solution incorrectly? This is extremely unhelpful.
Sam P.
23 September 2016
Using the SUVAT equations, we know a=9.8, u=0, v=7 and we are trying to find t. So we need the equation that links a, u, v and t which excludes s. The equation: v=u+atRearranging to find t: t= (v-u)/aSubstituting in the values: t=(7-0)/9.8So t=7/9.8= 0.71s (to 2 significant figures)
07 January 2017
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