Question

Suraj went to Big Bazaar to purchase certain goods . There he noticed an old lady struggling with her shopping. Immediately he showed her the lift and explained to her how it carries the load from one floor to the next. Even then the Old lady was not convinced. Then Suraj took her in the lift and showed her how to operate it. That old lady was very happy. a). What values does Suraj possess? b). A man of mass 80 kg stands on a weighing machine in a lift, which is moving (i) upwards with a uniform speed of 10 m/s. (ii) downwards with a uniform acceleration of 5 m/s2 (iii) upwards with a uniform acceleration of 5 m/s2 What would be the reading on the scale in each case?(Take g= 10 m/s2 )

Answer 1

Dear student,
Sooraj possess values of helping elders.
(a)Mass of the man, m = 80 kg

Acceleration, a = 0

Using Newton’s second law of motion, we can write the equation of motion as:

R – mg = ma

Where, ma is the net force acting on the man.

As the lift is moving at a uniform speed, acceleration a = 0

∴R = mg

= 80 × 10= 800 N

∴Reading on the weighing scale = 80kg

(b) Mass of the man, m = 80 kg

Acceleration, a = 5 m/s2 downward

Using Newton’s second law of motion, we can write the equation of motion as:

R + mg = ma

R = m(g – a)

= 80 (10 – 5) = 80 × 5

= 400 N

∴Reading on the weighing scale = 40kg

(c) Mass of the man, m =80 kg

Acceleration, a = 5 m/s2 upward

Using Newton’s second law of motion, we can write the equation of motion as:

R – mg = ma

R = m(g + a)

= 80 (10 + 5) = 80 × 15g

= 1200 N

∴Reading on the weighing scale = 120kg

Answer 2

$\huge\mathfrak\red{Elo!!}$

--- HERE'S THE SOLUTION ---
_______________

Sooraj possess values of helping elders.

(A) Mass of the man, m = 80 kg

Acceleration, a = 0

Using Newton’s second law of motion, we can write the equation of motion as:

R – mg = ma

Where, ma is the net force acting on the man.

As the lift is moving at a uniform speed, acceleration a = 0

∴R = mg

= 80 × 10= 800 N

∴ Reading on the weighing scale = 80kg
__________________

(B) Mass of the man, m = 80 kg

Acceleration, a = 5 m/s2 downward

Using Newton’s second law of motion, we can write the equation of motion as:

R + mg = ma
R = m(g – a)
= 80 (10 – 5) = 80 × 5
= 400 N

∴ Reading on the weighing scale = 40kg

_________________

(C) Mass of the man, m =80 kg

Acceleration, a = 5 m/s2 upward

Using Newton’s second law of motion, we can write the equation of motion as:

R – mg = ma
R = m(g + a)
= 80 (10 + 5) = 80 × 15g
= 1200 N

∴ Reading on the weighing scale = 120kg