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Use the KE and GPE equations to solve for speed or height depending on the situation.

 

A 1-kg model airplane has 12.5 joules of kinetic energy and 98 joules of gravitational potential energy. What is its speed? What is its height?

 Feb 5, 2019
 #1
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Answer:

speed: 5 m/s
height: 9.99 m 

Explanation:

KE=12mv2
kinetic energy = 12 * mass * velocity squared

12.5J=12⋅1kg⋅v2
1⋅v2=25J
v2=25J
v=±5J

since speed does not specify direction as velocity does, we can take the value of 5m/s for speed.

 

GPE=mgh
gravitational potential energy = mass * gravitational field strength * height

assuming the airplane is flying above Earth, the gravitational field strength is 9.81N/kg.

98J=1kg⋅9.81J⋅h

98J=9.81h

9.81h=98

h=989.81=9.99

h=9.99m 

 Feb 5, 2019
edited by itsyaboi  Feb 5, 2019

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