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Two crates of masses 120 kg and 65 kg are resting on a smooth horizontal surface - NSC Technical Sciences - Question 1 - 2021 - Paper 1
Question 1
Two crates of masses 120 kg and 65 kg are resting on a smooth horizontal surface. When a force of 600 N is applied on the 120 kg crate, the whole system accelerates,... show full transcript
Worked Solution & Example Answer:Two crates of masses 120 kg and 65 kg are resting on a smooth horizontal surface - NSC Technical Sciences - Question 1 - 2021 - Paper 1
Step 1
1.1 Which ONE of the following diagrams BEST represents a free-body diagram of ALL the forces acting on the 120 kg crate?
Answer
To determine the correct free-body diagram for the 120 kg crate, we need to consider the forces acting on it. The following forces act on the crate:
- The applied force of 600 N, directed to the right.
- The normal force (N) acting upward.
- The gravitational force (F₍g₎) acting downward.
- The force exerted by the 65 kg crate (F₆₅ₖg), acting to the left.
Based on these forces, the correct choice for the free-body diagram is:
D: This diagram accurately depicts all the forces acting on the 120 kg crate.
Step 2
1.2 How do the velocities at which they move away from each other compare? The velocity of the man is ... the velocity of the boy.
Answer
According to Newton's third law of motion, when the man and the boy push off against each other, they exert equal and opposite forces. However, their masses are different, which affects their acceleration.
The acceleration of each individual can be calculated using the formula:
Where:
- For the man, kg
- For the boy, kg
Because the force they exert is equal, the man, being heavier, will have a smaller acceleration compared to the boy, who is lighter and will accelerate more.
Thus, the velocity of the man will be less than the velocity of the boy.