Question

A lady of mass 80 kg stands on a weighing machine inside an elevator. find the readings of the weighing machine when; ( i ) the lift moves up at a constant speed of 8 m/s

Answer 1

Using equation for the second law of motion
R+ m*(-g)=ma
R - mg = ma
Here we have a=8 m/s2
R = m(a + g)
R= 80(8+10);taking g=10 m/s2
R = 1440N
Reding of weighing machine would be
1440/g ie 1440/10= 144kg

Answer 2

HÈLLØ!!

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$\Huge{\mathfrak{\red{\underline{QUESTION}}}}$

A lady of mass 80 kg stands on a weighing machine inside an elevator. Find the readings of the weighing machine when;

( i ) the lift moves up at a constant speed of 8 m/s

( ii ) the lift goes down at a constant acceleration of 4 ms-2

( iii ) the lift moves up with a constant acceleration of 4 ms-2

( iv ) the wires holding the lift break causing the lift to crash down.

$\Huge{\mathfrak{\blue{\underline{SOLUTION}}}}$

Given,

m = 80 kg, g = 10 ms-2

( i ) When the elevator moves up at a uniform speed, its acceleration is 0.

According to Newton’s second law of motion, the equation can be written as:

R – mg = ma

R = mg = 80 x 10 = 800N

Thus, the reading = 800/g = 80 kg

( ii ) Lift goes down at, a = 4ms-2

According to Newton’s second law of motion, the equation can be written as:

R +ma = mg

R = m (g –a) = 80 (10 – 4)

= 480 N

Thus, the reading = 480 / 10 = 48 kg

( iii ) Lift goes up at, a = 4 ms -2

According to Newton’s second law of motion, the equation can be written as:

R – mg = ma

R = m (g + a) = 80 (10 + 4)

= 1120 N

Thus, the reading = 1120/10 = 112kg

( iv ) When the lift crashes down freely , a = g

According to Newton’s second law of motion, the equation can be written as:

R + mg = ma

R = m (g – g) = 0. Thus, under a free fall condition the lady will be in a state of weightlessness.

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THÅÑKẞ!!