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Physics
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23 Nov 2019

I believe I have the first part worked out:
U=mgh --> U=980 K+U=0 --> K= -980
-980=.5(20)(v^2) --> v=9.9 m/s
But I have no idea where to go on the second part.

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Tod Thiel
Tod ThielLv2
3 Aug 2019

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

A Mini (mass m) and a Mack truck (mass M) travel on a curved,unbanked road of radius r. It can be assumed that the truck is muchmore massive than the car (M >> m) and that the coefficientsof friction (static, µs, and kinetic, µk) between the tires and theroad are the same for both vehicles.
a) Which vehicle can take the turn at the highest (constant) speedwithout slipping?
b) Derive an expression (in terms of the variables given) for themaximum speed that the vehicle of part (a) can take the turnwithout slipping.

I am assuming that the larger the mass, the larger the Fc required,and since friction is the same on both, that means the frictionthat is against the Fc on the car will be the same on the Fc of thetruck and because the Fc of the truck is bigger, the truck has ahigher chance to slip off, therefore the car can make the turn atthe highest constant speed without slipping. Is that correct?

For part b) I have an idea of where to start, but I am stuck:
Fc = mv^2/r
FcCar(r)/m = v^2
Root (Fc*r)/m = v
MAximum speed is when Fc is equal to FfrictionKinetictherefore:
N = Mass*acceleration = mass*(v/t)
ROOT [(Fc*r)/m] = uk*(m*v/t)
but I have no idea what to do now... Do I solve for v ?

A 16 kg child descends a slide 2 m high and reaches the bottom witha speed of 1.25 m/s. How much thermal energy due to friction wasgenerated in this process?


Known: m=16kg h=2.2m v=1.25m/s
Conservation of Energy
?K+?U+ {changes in all other forms of energy}=0
Ki+Ui+ {changes in all other forms of energy}= Kf+Uf+ {changes inall other forms of energy}
In this problem:
?K+?U+thermal energy=0
?K+?U=-thermal energy
?K=.5m(?v)^2 m=constant
?U=mg?h m & g are constants
Hence, mg?h+.5m(?v)^2=-thermal energy
mg?h=mg(0-2.2)=16*9.8*(-2.2)
.5m(?v)^2=m/2(1.25-0)^2
m/2(1.25-0)^2+16*9.8*(-2.2)=-thermal energy
8(1.25)^2+-344.96=-thermal energy
332.46 J =thermal energy

This is what I have so far. I am not sure of the sign of the finalanswer . Also could anyone point out any flaws . Other answers Ihave gotten are 257.46 ,-332.46, and --257.46. Any clarificationwould be nice.

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