Final Jeopardy Question

Momentum

500

100200300400

Forces

500400300200100

Energy

500400300200100

Electricity

100200300400500

A 20kg car moving 5m/s to the right crashes into a 45kg truck moving 10m/s to the left. Afterwards the truck is moving 4m/s to the right. Which direction and how fast is the car moving?

Back

20kg*5m/s + 45kg(-10m/s) = 45kg*4m/s + 20kg*v100kg*m/s – 450kg*m/s = 180kg*m/s + 20kg*v-350kg*m/s = 180kg*m/s + 20kg*v-530kg*m/s = 20kg*vV = (-530kg*m/s)/20kg = -26.5m/s

If a 20kg truck moving 15m/s to the right crashes into a 5kg car moving 20m/s to the left and they stick together, which direction and how quickly do they move?

20kg*15m/s + 5kg(-20m/s) = (20kg + 5kg) v300 kg*m/s – 100 kg*m/s = 25kg * v200 kg*m/s = 25kg*vV = 8 m/s to the right

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A 30kg truck is moving 5m/s to the right when it crashes into a 10kg car at rest. If the car moves 10m/s to the right, which direction and how fast does the truck move?30kg*5m/s = 30kg*v + 10kg*10m/s150kg*m/s = 30kg*v + 100kg*m/s50kg*m/s = 30kg*vV = 1.6m/s

Back

20kg*4m/s = 5kg*v80kg*m/s = 5kg*v

v=16m/s

A 20kg truck moving 4m/s crashes into a 5kg car at rest. If the truck stops, how fast does the car move?

Back

How much momentum does a 35kg car moving 14m/s have?

35kg*14m/s = 490 kg*m/s

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If a 20kg ball is compressed 4m in a spring (k=1000N/m) and released, how

fast will it move when it is 5m in the air? •SPE before = ½ 1000N/m * (4m)2

=500N/m*16m2 = 8000J Total Energy After = 8000J

GPE + KE after = 8000J20kg*10m/s/s*5m + 1/2*20kg*v2 =8000J

1000J + 10kg*v2 = 8000JV2 = 700m2/s2; v = sqrt 700 m/s Back

If a 10kg ball is moving 5m/s down when it is 10m high, how far will it compress a spring (k=200N/m) if 225J are lost as friction KE+ GPE - Friction → SPE1/2*10kg*(5m/s)2 + 10kg*10m/s/s*10m -

225J = SPE

125J + 1000J -225J =1/2(200N/m)x2

900J= 100N/m *x2

9m2 = x2; x=3m Back

How much force is required to stop a 10kg carMoving 4m/s in 4m

W=ΔKE; KE = ½ *10kg(4m/s)2

W = 80J = F*4mF=20N

Back

How fast would a 10kg sled on top of a 8m hill move when it reaches the bottom?

GPE → KE10kg*10m/s/s*8m → ½ 10kg v2

800J → 5kg * v2

160m2/s2--> v2

v=sqrt 160 m/s Back

How much kinetic energy does a 20kg car moving15m/s have?

½ 20kg*(15m/s)2 = 2250J

Back

A 75kg man is accelerating down 2m/s/sOn an elevator. What will a scale say he weighs?

Net force = 75kg*2m/s/s = 150N downFg = 75kg*10m/s/s = 750N downF up = 600N = reading on scale

Back

A 10kg object is being pulled by a spring (k=100N/m) that is causing it to accelerate up at 5m/s/s. How far is the spring stretched?Fnet= 5m/s/s*10kg = 50N up

Fdown = 100N, Fup = 150N100N/m * x = 150Nx=1.5m

Back

Fup =800N, Fdown =500N, net force = 300N upA=Fnet/m = 300N/50kg = 6m/s/s up

A 50kg person riding an elevator is on a scale.It says he weighs 800N. Which direction areThey accelerating and at what rate

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A 20kg object is hanging from a spring(k=20N/m). How far does it stretch?

Fdown=200N, Fup =200n200N = 20N/m * xX=10m

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Draw a free body diagram of a 100kg car driving 10m/s if there is 100N worth of friction.

Fup+down = 1000NFleft+right = 100N

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No, they are both positively charged

An atom with 8 protons, 7neutrons and 7 electrons is near an atom with 9 protons, 9 neutrons and 7 electrons. Are they attracted to each other?

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Draw an atom. Label the protons, neutrons and electrons

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An object with charge -6 is near an object with charge +2. What are their final charges and why?

-2,-2. 4 electrons flow

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180N * 1/9 = 20N

The electric force between two objects is 180N. If they are 3x as far apart, what is the force?

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What part of the atom carries negative charge? Positive charge?

Electrons, protons

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Identify as many units as you can (include what variable they go with) 100pts/unit

Distance-m Voltage - voltsVelocity –m/s Current - ampsAcceleration-m/s/s Wattage- wattsTime-s Charge - coulombsForce –N Spring Cons. - N/mEnergy – JMomentum – kg*m/s Back