HKEM & H2N - HUKUM KEKEKALAN ENERGI MEKANIK & HUKUM II NEWTON

Summary

The video introduces Newton’s Second Law and the Law of Conservation of Mechanical Energy, then demonstrates laboratory procedures for experiments related to both topics.

Newton’s Second Law

The learning goals are to understand Newton’s Second Law and how force and mass relate to an object’s acceleration.

The law is expressed as:

[ \sum F = ma ]

This means that an object’s acceleration is proportional to the net force acting on it. For the same net force, a larger mass produces less acceleration, and the acceleration is in the direction of the net force.

A soccer-ball example illustrates that a stronger kick gives the ball greater acceleration, so it travels farther in the same amount of time. In another example, a thrown stone initially moves upward due to the applied force. Gravity then slows it, brings it momentarily to a stop at its highest point, and accelerates it back downward.

Conservation of Mechanical Energy

Energy is described as the capacity to do work or cause change, and it is measured in joules. Energy can change form or be transferred—for example, heat can move from hot tea to a metal cup, or a moving ball can make a stationary ball move. Energy cannot be created or destroyed; it can only be transformed or transferred.

Mechanical energy is the sum of kinetic and potential energy:

[ E_p = mgh ]

[ E_k = \frac{1}{2}mv^2 ]

For a falling ball, potential energy is greatest at the top, while kinetic energy is greatest near the ground. Between those points, the ball has both forms of energy. Total mechanical energy remains constant when only conservative forces act on the system. Friction and other non-conservative forces can cause mechanical energy to change.

Practical Demonstration and Procedures

Equipment

The demonstration uses an air track and cart, photogates, a timer-counter, an air compressor, thread and a hook, hanging masses, and a cork or foam pad to catch the falling load.

Setup and Operation

• Place the first photogate at the 80 cm mark and the second at about the 50 cm mark, as shown later in the demonstration.
• Connect the photogate cables carefully to the timer-counter’s P1 and P2 ports. The cart should strike the first gate before the second.
• Leave the photogate cables connected until data collection is finished, and handle the connectors carefully.
• Place the cart on the air track while the compressor is off. Avoid rubbing or dragging the cart along the track.
• Make sure the cart’s hook faces upward so the thread does not slip off.
• Position a cork or foam pad beneath the hanging load to catch it.
• Set the timer-counter to the acceleration function. The presenter says to press the function button once to reset or select the function; it does not need to be cycled repeatedly.
• Turn on the air compressor for each trial. When finished, switch it off using its power button; there is no need to remove the cable.

Newton’s Second Law Trials (H2N)

For the first set of trials, a hanging load pulls the cart. The demonstration varies the load attached to the cart, including trials with no added load and trials with added masses.

For the second set, the cart is left without an added load while the mass on the hanger is varied. The examples use 5 g and 10 g; the hanger itself is also counted as part of the hanging mass.

The timer-counter records measurements for the trials. The video says the data collection and analysis will continue during the lab session.

Mechanical-Energy Data (HKM)

The presenter reuses data from the earlier H2N1 experiment rather than taking another set of measurements. In the example, a mass of 140 g is converted to 0.140 kg. The recorded times are T1 = 79.72 and T2 = 44.05; the subtitles do not specify their units.

The cart length is measured as 16.3 cm. Using the photogate positions, the presenter calculates:

[ H_1 = 80 - 16.3 = 63.7\text{ cm} ]

[ H_2 = 50 - 16.3 = 33.7\text{ cm} ]

These values are intended for later data analysis.

Speakers and Sources

• First presenter: Name rendered in the subtitles as Aislaa Mardah; assistant code SOD. She explains Newton’s Second Law and conservation of mechanical energy.
• Second presenter: Demonstrates the equipment and experimental procedures; identified by assistant code F. The subtitles do not clearly provide this presenter’s name.
• Other sources: No external speakers or named sources are featured.