Mindblown: a blog about philosophy.
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At What Speed is the Kinetic Energy the Same?
At what speed does a 1300 kg compact car have the same kinetic energy as a 1.8×104kg truck going 22 km/hr? Known variables: mass (m1): 1300kg v2=22km/hr m2= 1.8e4 1/2mv2 = 1/2mv2 (1300kg)(?)2 = (1.8e4)(222) (?)2=8712000/1300 Solve for the Unknown (?)2 = 6701.53 √6701.53 Vc= 82 km/hr
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How much Work is Done?
The two ropes shown in the bird’s-eye view of the figure are used to drag a crate 3.0 m across the floor. How much work is done by each of the three forces?
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Double Kinetic Energy
A car is traveling at 15 m/s 1) How fast would the car need to go to double its kinetic energy? Kinetic Energy(KE) = 1/2 m V2 The first part (1/2 m) doesn’t change, you need a new value for V such that V(new)2 = 2 x V(old)2 V(new) = (2 x 152) 1/2 V(new) = 4501/2…
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Gravitational Potential Energy
A 67 kg bike racer climbs a 1250 m-long section of road that has a slope of 4.3 By how much does his gravitational potential energy change during this climb? Since the biker starts on level ground, initial PE=0J The angle(θ) and hypotenuse length(h) given, we can calculate height. ΔU=mgh First is to find the height. The angle is given…
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How much Energy is Stored?
How much energy can be stored in a spring with k = 490 N/m if the maximum possible stretch is 20 cm? Known variables: k=490 x= 20cm or .2m Kinetic Energy Equation K.E= 1/2kx2 Once you know your variables and your equation, just plug it in. K.E= .5 x (490) x (.2)2 K.E= 9.8 J
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How much Thermal Energy is Created?
Marissa drags a 22 kg duffel bag 16 m across the gym floor. If the coefficient of kinetic friction between the floor and bag is 0.15 , how much thermal energy does Marissa create? Known variables: mass (m)= 22 kg drag (s)=16 m coefficient of kinetic friction=(μ) .15 gravity (g)= 9.8 thermal energy equation: μ*m*g*s μ …
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Minimum Speed
With what minimum speed must you toss a 100 ball straight up to hit the 14 -high roof of the gymnasium if you release the ball 1.4 above the ground? Solve this problem using energy. Work is the same as change in energy You can figure out how much gravitational potential energy the ball has…
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What is the Landing Speed?
As a 15000 kg jet plane lands on an aircraft carrier, its tail hook snags a cable to slow it down. The cable is attached to a spring with spring constant 60000 N/m. If the spring stretches 30 m to stop the plane, what was the plane’s landing speed? Variables known: m= 15000 kg k= 60000 N/m…
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How much Work?
1) How much work does an elevator motor do to lift a 1000 kg elevator a height of 100 m? Known variables: mass (m): 1000 kg height (h): 100m Work = Force x Distance We need to find a force. Since there is gravity, all we have to do is multiply it by the mass…
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Final Velocities : Elastic
Ball 1, with a mass of 100 g and traveling at 15 m/s, collides head on with ball 2, which has a mass of 350 g and is initially at rest. What are the final velocities of each ball if the collision is perfectly elastic? Known variables: Mass(m1) of the first ball = 100 g or .100 kg Initial velocity (v1) of…
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