Question

A body of a mass 40 kg stands on a weighing machine in an accelerated lift. The
reading on the scale of the weighing machine is 300 N. Find the magnitude and
direction of acceleration.
(a) 2.3 m/s2 upwards
(b) 2.3 m/s2 downwards
(C) 4.6 m/s2 upwards
(d) 4.6 m/s2 downwards​

Answer 1

the correct answer is option B.

2.3m/s² downwards

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Answer 2

Answer:

Correct magnitude and direction of acceleration of lift are:

• 2.3 m/s², downwards

Explanation:

Mass of body is, m = 40 kg

so,

Actual weight of body will be,

→ W = m g = (40) · (9.8) = 392 N

and, It is given that weighing Machine is reading weight of body as 300 N in an accelerating lift.

So,

we can see that while motion of lift Weight of body is decreasing, it means Lift is accelerating in downward direction.

Now

Let, magnitude of acceleration of lift be a

then

Since, Lift is accelerating downward

therefore tension (T) in the lift cable would be

→ T = m g - m a

→ 300 = ( 40 ) ( 9.8 ) - ( 40 ) ( a )

→ 300 = 392 - 40 a

→ 300 - 392 = -40 a

→ - 92 = - 40 a

→ a = 2.3  m/s²

Therefore,

• Magnitude of acceleration of lift would be 2.3 m/s²., and direction would be downwards.

Hence,

OPTION (b) is correct.