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
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.
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)