As the reference height is at B, so above that reference height is considered positive, and below the reference height it is considered negative. Hence the height-time graph is as such. Consider a vertical oscillating object, similar to the simple pendulum, the middle is the fastest.

To get a sharp image on the screen, there are various methods and concepts that you have learned and can be applied here. View the video for the explanation:

There is a related question in Pure Physics 2021 P2 Q9, but slightly different. It asked about why home circuit of 230V is not suitable...

Refer to the video below for the explanation. Related post: Velocity-time graph of ball released from rest with air resistance - Part 1...

Refer to the video below to understand how to sketch the graph. For O-Level, we just need to focus on the general shape. 2024PP Paper 2...

Internal energy of a substance is the sum of kinetic energy and  potential energy of the molecules. kinetic energy  is directly...

In the syllabus, we are required to understand the orders of magntiude of various objects. Though we may no need to memorise the exact...

Fleming's Right-Hand Rule is another useful rule for understanding electromagnetic induction. This rule helps us determine the direction...

Flemeng's Left Hand Rule, using your left hand, with the thumb, 1st finger and 2nd finger all 90 degrees to one another. This is covered...

Drawing ray diagrams for converging lens come in many forms. But the basic concepts needed are the 3 rays (which have rules to follow) to...