For each of these problems, don\'t just write down an answer, even if you can so
ID: 1618825 • Letter: F
Question
For each of these problems, don't just write down an answer, even if you can solve it in your head. Briefly justify your answer by writing down the physics relationship or equation you're using to think about it. a) To make a stuck bolt turn, you have to apply 120 N of force to a wrench 10 cm long. How much force would you have to apply to a wrench 30 cm long? b) An industrial flywheel spinning at 700 RPM stores enough kinetic energy to power a particular machine for 1 minute. For how long could it power the machine if it were spinning at 1400 RPM? c) In the process of becoming a neutron star, a star of mass M and initial radius R rapidly collapses to a radius of R/100. If it rotates once every T seconds before it collapses, how long does it take to rotate once after it collapses? d) Starting from rest, a hollow, thin-walled, 33-gram cylinder of radius 4 cm rolls down a ramp and reaches a final speed of 20 cm/s. What would the final speed of a 33-gram cylinder of radius 8 cm be?Explanation / Answer
Q1. a. To make a stuck bolt turn, 120 N of force need to be applied to a wrench of 10 cm(=0.1m) long.
So torque required = force x length = 120 x 0.1 =12 N.m
In order to get the same torque with 30 cm long wrench, force to be applied = torque required/ length of wrench
=12/0.3 = 40 N
so 40 N is required to apply to a 30 cm wrench length.
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