Answer:
5 feet
Explanation:
First lets imagine that the values are in meters and kg, to make it easier for me.
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The force created by the teacher is 120 × 5 = 600N.
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The force created by the 50 kg student is 50 × 8 = 400N
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The force that needs to be created by the 40 kg student is 600N - 400N = 200N.
To create that force that student needs to sit 200 ÷ 40 = 5m.
So the 40 lbs student is sitting 5 feet from the fulcrum.
B-friction acts in direction opposite to objects motion
It doesn't matter what the object's initial velocity is, or how long
the acceleration lasts. All that matters is the object's mass and
acceleration.
Force = (mass) x (acceleration) =
(5kg) x (15 m/s²) =
75 kg-m/s² = <em>75 newtons .</em>
Answer:
a)
= 928 J
, b)U = -62.7 J
, c) K = 0
, d) Y = 11.0367 m, e) v = 15.23 m / s
Explanation:
To solve this exercise we will use the concepts of mechanical energy.
a) The elastic potential energy is
= ½ k x²
= ½ 2900 0.80²
= 928 J
b) place the origin at the point of the uncompressed spring, the spider's potential energy
U = m h and
U = 8 9.8 (-0.80)
U = -62.7 J
c) Before releasing the spring the spider is still, so its true speed and therefore the kinetic energy also
K = ½ m v²
K = 0
d) write the energy at two points, maximum compression and maximum height
Em₀ = ke = ½ m x²
= mg y
Emo = 
½ k x² = m g y
y = ½ k x² / m g
y = ½ 2900 0.8² / (8 9.8)
y = 11.8367 m
As zero was placed for the spring without stretching the height from that reference is
Y = y- 0.80
Y = 11.8367 -0.80
Y = 11.0367 m
Bonus
Energy for maximum compression and uncompressed spring
Emo = ½ k x² = 928 J
= ½ m v²
Emo =
Emo = ½ m v²
v =√ 2Emo / m
v = √ (2 928/8)
v = 15.23 m / s