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.
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.
