There are two monkeys A and B of masses 6 kg and 3 kg respectively. Monkey B is holding the tail of monkey A. Monkey A is trying to climb the rope as shown in the figure. The tail of monkey A can tolerate the maximum tension of 45 N. Find the minimum and the maximum force that monkey A should apply on the rope in order to carry the monkey B with it. (Take g = 10 m/sec2)
There are two monkeys A and B of masses 6 kg and 3 kg respectively. Monkey B is holding the tail of monkey A. Monkey A is trying to climb the rope as shown in the figure. The tail of monkey A can tolerate the maximum tension of 45 N. Find the minimum and the maximum force that monkey A should apply on the rope in order to carry the monkey B with it. (Take g = 10 m/sec2) Correct Answer 90 N and 135 N
CONCEPT:
Newton's second law of motion
- According to Newton's second law of motion, the rate of change of momentum of a body is directly proportional to the applied unbalanced force.
- The magnitude of the force is given as,
⇒ F = ma
Where F = resultant force, m = mass and a = acceleration
CALCULATION:
Given mA = 6 kg, mB = 3 kg, Tf = 45 N, and g = 10 m/sec2
Let the maximum possible acceleration that monkey A can apply to be "a".
- The free body diagram of monkey B is drawn as,
[ alt="F1 Shraddha Prabhu 07.09.2021 D2" src="//storage.googleapis.com/tb-img/production/21/09/F1_Shraddha_Prabhu_07.09.2021_D2.png" style="width: 66px; height: 187px;"> -----Figure (1)
From figure 1,
⇒ Tf = mBa + mBg
⇒ 45 = 3a + (3 ×10)
⇒ a = 5 m/sec2 -----(1)
- The free body diagram of monkey A is drawn as,
Let the tension in the rope be T due to acceleration "a".
[ alt="F1 Shraddha Prabhu 07.09.2021 D3" src="//storage.googleapis.com/tb-img/production/21/09/F1_Shraddha_Prabhu_07.09.2021_D3.png" style="width: 66px; height: 204px;"> -----Figure (2)
From figure 2,
⇒ T = mAa + mAg + Tf
⇒ T = (6 × 5) + (6 × 10) + 45
⇒ T = 30 + 60 + 45
⇒ T = 135 N
- This tension is the maximum force that monkey A can apply safely in order to carry monkey B with it.
For the condition of minimum force, there will be no acceleration in Monkey A and B,
∵ a = 0 m/sec2
⇒ Fmin = mAg + mBg
⇒ Fmin = (6 × 10) + (3 × 10)
⇒ Fmin = 90 N
- So the minimum and the maximum force that monkey A should apply on the rope in order to carry the monkey B with it are 90 N and 135 N respectively. Hence, option 3 is correct.