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marishachu [46]
3 years ago
11

A fat person weighing 80 Kg falls on a concrete floor from 2m. If whole of the mechanical energy is converted into heat energy,

then heat produced in SI units will be nearly
Physics
1 answer:
sasho [114]3 years ago
4 0

Answer:

The heat produced is 1568 J

Explanation:

The given parameters are;

The mass of the person, m = 80 kg

The height from which the person falls, h = 2 m

Mechanical Energy, ME = Potential Energy, PE + Kinetic Energy, KE

At the height, from where the person falls, the initial velocity of the person = 0 m/s

Therefore;

The initial kinetic energy, K.E. = 1/2·m·v² = 1/2 × 80 kg × (0 m/s)² = 0 J

From which we have;

The Mechanical Energy, M.E. = The initial Potential Energy, P.E. + 0 J

∴ The Mechanical Energy, M.E. = The initial Potential Energy, P.E.

The initial Potential Energy, P.E. = m·g·h

Where;

m = The mass of the person

g = The acceleration due to gravity ≈ 9.8 m/s²

∴ The initial Potential Energy, P.E. = 80 kg × 9.8 m/s² × 2 m = 1568 J

The Mechanical Energy, M.E. = The initial Potential Energy, P.E. = 1568 J

The whole mechanical energy is converted into heat energy, therefore, we have;

The Mechanical Energy, M.E. = The heat energy = 1568 J

The heat produced = The heat energy = 1568 J.

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A 5-cm-high peg is placed in front of a concave mirror with a radius of curvature of 20 cm.
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Answer:

Explanation:

Using the magnification formula.

Magnification = Image distance(v)/object distance(u) = Image Height(H1)/Object Height(H2)

M = v/u = H1/H2

v/u = H1/H2...1

3) Given the radius of curvature of the concave lens R = 20cm

Focal length F = R/2

f = 20/2

f = 10cm

Object distance u = 5cm

Object height H2= 5cm

To get the image distance v, we will use the mirror formula

1/f = 1/u+1/v

1/v = 1/10-1/5

1/v = (1-2)/10

1/v =-1/10

v = -10cm

Using the magnification formula

(10)/5 = H1/5

10 = H1

H1 = 10cm

Image height of the peg is 10cm

4) If u = 15cm

1/v = 1/f-1/u

1/v = 1/10-1/15

1/v = 3-2/30

1/v = 1/30

v = 30cm

30/15 = H1/5

15H1 = 150

H1/= 10cm

5) if u = 20cm

1/v = 1/f-1/u

1/v = 1/10-1/20

1/v = 2-1/20

1/v = 1/20

v = 20cm

20/20 = H1/5

20H1 = 100

H1 = 5cm

6) If u = 30cm

1/v = 1/f-1/u

1/v = 1/10-1/30

1/v = 3-1/30

1/v = 2/30

v = 30/2 cm

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15/30 = Hi/5

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Answer: 154.08 m/s

Explanation:

Average acceleration a_{ave} is the variation of velocity  \Delta V over a specified period of time  \Delta t:

a_{ave}=\frac{\Delta V}{\Delta t}}

Where:

a_{ave}=1.80 m/s^{2}

\Delta V=V_{f}-V_{o} being V_{o}=0 the initial velocity and V_{f} the final velocity

\Delta t=85.6 s

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a_{ave}=\frac{V_{f}-V_{o}}{\Delta t}}

Since V_{o}=0:

a_{ave}=\frac{V_{f}}{\Delta t}}

Finding V_{f}:

V_{f}=a_{ave} \Delta t

V_{f}=(1.80 m/s^{2})(85.6 s)

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Explanation:

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