You have just joined an exclusive health club, located on the top floor of a sky

Question

You have just joined an exclusive health club, located on the top floor of a skyscraper. You reach the facility by using an express elevator. The elevator has a precision scale installed so that members can weigh themselves before and after their workouts. A member steps into the elevator and gets on the scale before the elevator doors close. The scale shows a weight of 187.5 lb. Then the elevator accelerates upward with an acceleration of 2.40 m/s2, while the member is still standing on the scale. What is the weight shown by the scale's display while the elevator is accelerating?

231 lb

232 lb

233 lb

234 lb

231 lb

232 lb

233 lb

234 lb

Explanation / Answer

Acceleration due to gravity is g = 9.8 m/s2

initially when the lift is at rest, the weight shown is m*g = 187.5

m = 187.5 / 9.8

acceleration of the lift a = 2.4 m/s2

when the lift is accelerating then the effective weight or the apparent weight is m*(g + a)

so the weight shown while lift moving up is (187.5 / 9.8) * (9.8 + 2.4) = 233.4 lb

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