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  1. F

    Refrigerator and Heat Pump

    Allright i got it now.. since 1kWh = 3.6MJ (which is 3600000J) 1.25kWh X 36000000 = 4.5 X 10^6 Joules.. thanks for the help...
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    Refrigerator and Heat Pump

    okay i might have misunderstood. i'm so sorry..what conversion is being made? is it from kWh to Joules or what? if so how so??
  3. F

    Refrigerator and Heat Pump

    okay.. but converting the unit still gives a wrong answer...
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    Refrigerator and Heat Pump

    Homework Statement A freezer has a coefficient of performance of 6.30. It is advertised as using electricity at a rate of 457kWh/yr. a)On average how much energy does it use in a single day? b) What maximum mass of water at 20.0 degree celsius could the freezer freeze in a single day...
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    Center of mass for a raft

    yeah its perfectly okay now.. Thanks a bunch for figuring it out.
  6. F

    Center of mass for a raft

    ohh.. that would be half the distance right?... which is 9m
  7. F

    Center of mass for a raft

    Well i think that the raft has (0,0) the NE car has (18,18) the SE car has (18,-18) the SW car has (-18,-18)
  8. F

    Center of mass for a raft

    Okay... i already had that in mind while drawing up that solution. Am i missing something??
  9. F

    Center of mass for a raft

    Homework Statement A square uniform raft, 18m by 18m of mass 6200kg is used as a ferry boat. if three cars each of mass 1350 kg occupy the NE, SE, and SW corners, determine the Centre of mass of the loaded ferryboat relative to the centre of the raft Homework Equations Center of mass...
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    Mechanical energy- Falling rock

    Okay; thanks for verifying !!!
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    Mechanical energy- Falling rock

    Homework Statement If the original height of a falling rock is y1 = h = 3.0m; calculate the rock's speed just before it hits ground. Homework Equations From conservation of mechanical energy law 1/2mv1^2 + mgy1 = 1/2mv2^2 + mgy2 The Attempt at a Solution I think i'm supposed to find v2 i.e...
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    Calculating Work done

    yeah.. it is m/s^2 .. my mistake thanks
  13. F

    Calculating Work done

    Homework Statement A box of mass 6.0kg is accelerated from rest by a force across the floor at a rate of 2.0m/s for 7.0s. Find the net work done on the box. Homework Equations Work done = Force x distance The Attempt at a Solution F = ma F = 6 x 2 = 12N i solved for final...
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    Projectile motion of a kicked ball

    Homework Statement A ball is kicked in the air with an initial velocity of 15m/s at an angle of 37 degrees; 0.8 m above the ground. How long is the ball in the air???? Homework Equations The Attempt at a Solution I resolved the vector into its components and the y component was...
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    Vector and magnitude problem

    i think x would be zero right??? if dat's right what wuld y be?? Also ur notation is a bit confusing.. what is the vector A?? Also the vector in the positive y direction is supposed to be the resultant vector i.e B + C BUT u wrote B + A..i'm kinda confused there..
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    Vector and magnitude problem

    Homework Statement A little assistance with this question:- A vector, B, when added to the vector C = 3i + 4j yields a resultant vector which is in the positive y direction and has a magnitude equal to that of C. What is the magnitude of B? Homework Equations The Attempt at a...
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    Motion in one dimension

    Yeah, i know displacement is change in position... but am trying to find the distance first; because the question asks for both distance and displacement and i think we need to find the distance before we can get the displacement.. isn't that right???
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    Motion in one dimension

    Homework Statement A car travels north at 30 m/s for one half hour. It then travels south at 40 m/s for 15 minutes. The total distance the car has traveled and its displacement are??? Homework Equations The Attempt at a Solution First of all i converted from m/s to km/h. I...
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    Motion in one dimension

    Oh thanks very much....
  20. F

    Motion in one dimension

    Hello, please any help will be very much appreciated; A bullet is fired through a board, 14.0 cm thick, with its line of motion perpendicular to the face of the board. If it enters with a speed of 450 m/s and emerges with a speed of 220 m/s, what is the bullet's acceleration as it passes...
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