A student catches a falling ruler after it has fallen 17 cm…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student catches a falling ruler after it has fallen cm. Use .
- What is the reaction time in seconds?
- What is it in milliseconds?
- How far would the ruler fall in s, in centimetres?
Need a reminder? The key ideaShow
A reflex is an involuntary response that needs a part of the CNS. The reflex arc has at least one afferent neuron, which enters the CNS by a dorsal root, and one efferent neuron, which goes to the effector. Time equals distance divided by speed, and each chemical synapse adds about . A body falling from rest covers .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. cm m. .
Plan. Solve for . We want , so .
Step 1. Time. s, which is about s.
Step 2. In milliseconds. ms.
Step 3. Fall in s. m cm.
Answer: s; ms; cm.
Check. The reaction time of a voluntary action is about ten times longer than a reflex.
Watch out. Use metres in the formula. Mixing cm and m is the usual error.
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