Video Instruction
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Ex 2) A 10 kg frictionless cart is resting on a horizontal table. A force of 10 N is applied to the cart for a distance of 8 m. What is the carts new KE? |
Ex 2) A 10 kg frictionless cart is resting on a horizontal table. A force of 10 N is applied to the cart for a distance of 8 m. What is the carts new kinetic energy?
m = 10 kg
F = 10 N
d = 8 m
KE = (˝)mv2 ??
ΔKE = W
= Fd = 10N(8m)
= 80 Nm
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Ex 3) 100 Joules of work is needed to lift a 100 kg object from the ground.
What is the objects new P.E.? |
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Ex 3) 100 Joules of work is needed to lift a 100 kg object from the ground.
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What is the objects new P.E. ? |
W = ΔPE = 100J
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Ex 4) Crate is pulled 6.00 m up an incline with a force of 50.0 N. P.E. of cart increases by 250. J. Total work done against friction? |
Ex 4) Crate is pulled 6.00 m up an incline with a force of 50.0 N. If the PE of the cart increases by 250. J. , what is the total work done against friction?
d = 6.00 m
F = 50.0 N
ΔPE = 250. J
W = Fd = 50.0 N(6 m)
= 300. J
W = ΔPE + Wf
300. J = 250. J + Wf
Wf = 50.0 J
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Ex 5) 4 N is exerted on a 1 kg mass at rest for 2 m, causing it to move
A. Find the objects K.E. |
KE = (1/2)mv2
Work on object = ΔKE
ΔKE = W = Fd = 4 N(2 m)
= 8 Nm
B. Find the objects velocity
KE = (1/2)mv2
8 Nm = (1/2)1 kg(v2)
16 = v2
V = 4 m/s
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Ex 6) A force of 100.0 N lifts the object 10.00 m off the ground. What is the object's new PE? What is the mass of the object? |
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Ex 6) A force of 100.0 N lifts the object 10.00 m off the ground. What is the object's new potential energy?
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mass of object? |
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ΔPE = W = Fd
= 100.0 N(10.00 m)
= 1000. Nm
What is the mass of the object?
PE = 1000. J = mgh
= m(9.8 m/s2)10.00 m = 1000. J
m = 10.20 kg
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Ex 7) Spring has a spring constant of 2.0 N/m.
How much work must be done to stretch 5.0 m from its equilibrium position? |
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Ex 7) A spring has a spring constant of 2.0 N/m. How much work must be done to stretch it 5.0 m from its equilibrium position?
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k = 2.0 N/m x = 5.0 m W = ? |
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W = PE = 1/2kx2
= (1/2)2.0 N/m(5.0 m)2
= 25. J
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Ranking
Rank the KE of the car from largest to smallest
B, C, D, A
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Task
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How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s? A) 4X as far B) 2 X as far |
Review
Name the energy conversion that
occurs in a Grandfather clock.
School blocks Youtube? Download file below.
St. Mary's Physics YouTube Channel
PE of the hanging weights
converts to the KE of the clock
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Static Electricity |
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Enrichment
Superfluids
The strange behavior of liquid helium
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