2003 AIPMT Laws of MotionApparent Weight in a Lift Easy Question 62 of 72 in Laws of Motion

A man weighs 80 kg. He stands on a weighing scale in a lift which is moving upwards with a uniform acceleration of 5 m/s$^2$. What would be the reading on the scale ? (g = 10 m/s$^2$)

A Zero
B 400 N
C 800 N
D 1200 N

The answer is D.

Solution

The scale reads the normal reaction N exerted on the man.
For the man moving up with acceleration a: $N - mg = ma$
Reading of weighing scale $= N = m(g + a)$
$= 80(10 + 5) = 80 \times 15 = 1200$ N
So the scale reads 1200 N (more than his true weight of 800 N).

Concept Apparent weight in accelerating lift

Laws of Motion in past papers

72 questions from this chapter have appeared across 27 exam years.