NECO 2023 · Paper 1 · Q40

A 50 kg bag of rice is placed in a lift which moves with an upward acceleration of 8 ms−28\text{ ms}^{-2}. What is the reaction between the floor of the lift and the rice? [Take g=10 ms−2g = 10\text{ ms}^{-2}]

Worked solution (try it first)
  1. The forces on the rice are the reaction RR upwards and the weight mgmg downwards.
  2. The acceleration is upwards, so R−mg=maR - mg = ma.
  3. So R=m(g+a)=50(10+8)R = m(g + a) = 50(10 + 8), which is 900 N, option C.

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