00:01
In this question we have been told that a 10 kg block is at a height of 7 m above the ground and it slides down an incline to the ground.
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Assuming there is no friction between the block and the incline and the coefficient of friction between the block and the ground is 0 .12, in part a we need to find out the potential energy of the block at the top of the incline.
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So in part a we need to find out the potential energy.
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So the formula for potential energy is mgh mass into gravitational acceleration into height.
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We know the mass of the block which is 10.
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We know the gravitational acceleration which is 9 .8 meter per second square and we know the height which is 7.
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So this gives us a value of 686 joules.
00:47
So that is the answer for part a.
00:49
Now in part b we need to find out the potential energy of the block at the bottom of the incline.
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So as you can see the block will follow this path.
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It will move down the incline and we know there is no frictional forces acting on the incline.
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So it will get at this point.
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So we need to find out the potential energy at the bottom of the incline at this point.
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So as you can see the block is now on the ground level which means its height is going to be 0.
01:23
So again we are going to use the same formula but in this case the height is going to be 0.
01:30
So the whole value multiplied by 0 is going to be 0.
01:33
So this is going to be 0 joules.
01:35
The potential energy of the block at the bottom of the incline is going to be 0.
01:40
Now let's continue.
01:44
In part c we need to find out the kinetic energy of the block at the top of the incline.
01:52
So the formula for kinetic energy is ke is half mb square.
01:59
Now in this question if you read the question we have been told that a 10 kg block is at rest at a height of 7 meter which means its initial velocity is going to be 0.
02:10
So again in this formula we know the mass and we know the velocity which is 0 because it is initially at rest at the top of the incline.
02:19
So the kinetic energy again going to be 0 joules.
02:23
Now in part d we need to find out what is the kinetic energy of the block at the bottom of the incline.
02:32
So to find out the kinetic energy we are going to use a conservation of energy.
02:36
We know that there is no frictional forces acting on the incline so work done due to friction is going to be 0.
02:43
So the conservation of energy that the energy of the block at the top of the incline is going to be equal to energy of the block at the bottom of the incline.
02:56
So at the top the kinetic energy is going to be 0 as we have calculated and the potential energy is 686.
03:09
We are going to write down its value and at the bottom the potential energy is 0 and the kinetic energy is ke plus 0.
03:21
So using this formula 686 is going to be equal to the kinetic energy at the bottom.
03:28
So the formula for kinetic energy is as you can remember half mv square.
03:34
So half mv square this is the velocity at the bottom.
03:38
I am going to write down b...