Distance in the nth second
"Distance in the nth second" is a free, interactive Class 11 Physics simulation for NEET and JEE, built on the NCERT section "Free fall and vertical motion under gravity" in Motion in a Straight Line. A body starting with speed u and acceleration a: strobe marks each second and bars show distance in each second, s_n = u + a(n − ½), giving 1:3:5:7 from rest. NEET has asked about this idea 2 times in 10 years of papers. JEE Main asked 30 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Free fall and vertical motion under gravity in Motion in a Straight Line. Change the values and watch what happens.
What it shows
NCERT § Kinematic equations
A body starting with speed u and acceleration a: strobe marks each second and bars show distance in each second, s_n = u + a(n − ½), giving 1:3:5:7 from rest.
Controls
3 to try
- Sliderinitial speed u 0–20 m/s
- Slideracceleration a 1–10 m/s²
- Sliderwhich second n 1–8 (highlighted)
Try this
Starting from rest, set a so that the body covers exactly 45 m during the 5th second (a = 10 m/s²).
Common mistake
Confusing distance in the nth second with distance in n seconds.
In NEET
10 years of papers
Asked 2 times in 10 years of NEET.
See the past questions: Kinematics in 1D, Motion in a Straight Line (chapter)
In JEE Main
42 shifts analysed
30 questions from Motion in a Straight Line across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Kinematic Equations for Uniformly Accelerated Motion"
- Near the earth's surface, with air resistance neglected, every body has the same downward acceleration g ≈ 9.8 m s⁻², whatever its mass.
- If upward is taken positive, a = −g throughout the flight, on the way up, at the top and on the way down.
- A body released from rest falls a distance ½gt² in time t, and its speed after falling a height h is √(2gh).
- A body thrown up with speed u rises to a height u²/2g in time u/g; with no air resistance it takes the same time to come down to the launch level and returns with the same speed.
- When a body is thrown up from a height above the ground, use one equation from launch to landing with the landing displacement taken as negative; there is no need to split the flight.
- Galileo's law of odd numbers: for a body starting from rest with constant acceleration, distances covered in successive equal time intervals are in the ratio 1 : 3 : 5 : 7 and so on.
- In free fall, v plotted against t is a straight line with slope −g (upward positive), while x plotted against t is a parabola.
Questions
5 answers
- What does the "Distance in the nth second" simulation show?
- A body starting with speed u and acceleration a: strobe marks each second and bars show distance in each second, s_n = u + a(n − ½), giving 1:3:5:7 from rest.
- What mistake does the "Distance in the nth second" simulation fix?
- A common mistake it clears up: confusing distance in the nth second with distance in n seconds.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 2 times in 10 years of papers.
- Does JEE Main ask questions from Motion in a Straight Line?
- Yes. JEE Main asked 30 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Free fall and vertical motion under gravity" in Motion in a Straight Line (Class 11 Physics).
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