Pembahasan Materi Penerapan Hukum Newton pada Lift

Summary

This video explains the application of Newton's laws to an elevator's motion, focusing on the forces acting on a person inside. When the elevator is at rest, Newton's 1st law states that the normal force equals the person's weight. As the elevator moves upwards, Newton's 2nd law shows that the normal force increases, as the floor exerts greater pressure. Conversely, when the elevator moves down, the normal force decreases. The video clearly demonstrates how the normal force changes based on the elevator's motion, providing a practical understanding of Newton's laws in everyday life.

Takeaways

• 😀 When the elevator is at rest, Newton's First Law applies, and the sum of forces acting on the person is zero (ΣF = 0).
• 😀 The forces acting on the person in a stationary elevator include the downward gravitational force (weight) and the upward normal force from the elevator floor.
• 😀 When the elevator is at rest, the normal force (N) is equal to the person's weight (W = m * g).
• 😀 As the elevator moves upward, the normal force increases because the floor applies more pressure to the person.
• 😀 Newton's Second Law (ΣF = m * a) applies when the elevator is moving upward, with the forces acting in the same direction as the motion.
• 😀 The normal force when moving up is equal to the person's mass multiplied by acceleration (N = m * a + m * g).
• 😀 When the elevator moves downward, Newton's Second Law still applies, but the forces are reversed in direction.
• 😀 In the downward motion of the elevator, the normal force decreases as the elevator moves downward, since the upward force is reduced.
• 😀 When moving down, the normal force is given by N = m * g - m * a, with the magnitude of the normal force being smaller.
• 😀 Three conditions for the elevator's effect on normal force: at rest (N = W), moving up (N > W), and moving down (N < W).

Q & A

What is Newton's 1st Law, and how does it apply when the elevator is at rest?

Newton's 1st Law states that an object at rest stays at rest unless acted upon by an external force. In the case of the elevator at rest, the net force acting on the person is zero, meaning the normal force from the elevator floor equals the gravitational force (weight) of the person.

What happens to the normal force when the elevator starts moving upwards?

When the elevator moves upwards, the normal force increases. This is because the elevator floor applies additional pressure on the person to accelerate them upwards, which results in an increase in the normal force.

How does Newton's 2nd Law apply when the elevator is moving upwards?

Newton's 2nd Law, which states that the net force equals mass times acceleration (Sigma F = m * a), applies when the elevator moves upwards. The normal force acts in the same direction as the motion (upward), while the gravitational force acts downward. The normal force is greater than the person's weight to account for the upward acceleration.

What is the equation that represents the forces acting on the person when the elevator is moving upwards?

The equation when the elevator is moving upwards is: N = m * (a + g), where N is the normal force, m is the mass of the person, a is the acceleration of the elevator, and g is the acceleration due to gravity.

What happens to the normal force when the elevator moves downwards?

When the elevator moves downwards, the normal force decreases because the elevator is accelerating in the downward direction. The floor of the elevator applies less pressure on the person as they experience less upward force.

How does Newton's 2nd Law apply when the elevator is moving downwards?

When the elevator moves downward, Newton's 2nd Law states that the net force is equal to the mass of the person multiplied by the downward acceleration (Sigma F = m * a). The normal force is reduced to account for the downward motion of the elevator.

What is the equation for the forces when the elevator is moving downwards?

The equation when the elevator is moving downwards is: N = m * (g - a), where N is the normal force, m is the mass of the person, g is the acceleration due to gravity, and a is the downward acceleration of the elevator.

Why does the normal force decrease when the elevator moves downward?

The normal force decreases when the elevator moves downward because the downward acceleration reduces the pressure exerted by the elevator floor on the person. The net force acting on the person is adjusted to account for this downward motion.

What is the relationship between the weight of the person and the normal force when the elevator is at rest?

When the elevator is at rest, the normal force acting on the person is equal to the person's weight. The upward normal force cancels out the downward gravitational force, resulting in no net force on the person.

How does the magnitude of the normal force change based on the elevator's motion?

The magnitude of the normal force is equal to the weight of the person when the elevator is at rest. When the elevator moves upwards, the normal force increases, and when it moves downwards, the normal force decreases due to the elevator's acceleration in either direction.