An object of mass 20 kg is dropped from a height ‘h’ metres as shown in the tables below.

(g = 10 m/s2)

Table A

Height from which an object is dropped

‘h’ (m)

Velocity of an object falling from the height

‘v2’ (m/s2)

10

0

2

80

Table B

Height from which an object is dropped

‘h’ (m)

Velocity of an object falling from the height

‘v2’ (m/s2)

10

0

2

40

 

Which of the above tables has wrong data in terms of the law of conservation of energy of an object falling from height ‘h’ metres?

Asked by Topperlearning User | 9th Nov, 2016, 03:51: PM

Expert Answer:

Table A: 

Height from which an object is dropped

‘h’ (m)

Velocity of an object falling from the height

‘v2’ (m/s2)

Potential energy

mgh (J)

Kinetic energy

½mv2 (J)

TE =

PE + KE

10

0

20 × 10 ×10 = 2000

½ × 20 × 0 = 0

2000

2

80

20 × 10 ×2 = 400

½ × 20 × 80 = 800

1200

 

Table B:

Height from which an object is dropped

‘h’ (m)

Velocity of an object falling from the height

‘v2’ (m/s2)

Potential energy

mgh (J)

Kinetic energy

½mv2 (J)

TE =

PE + KE

10

0

20 × 10 × 10 = 2000

½ × 20 × 0 = 0

2000

2

40

20 × 10 × 2 = 400

½ × 20 × 40 = 400

800

According to the law of conservation of energy, the sum of the potential energy and kinetic energy of the object should remain the same at every point during its fall.

Answered by  | 9th Nov, 2016, 05:51: PM

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