Physics · Class 11

Inertia trolleys

Mass measures resistance to a change in velocity. A net force accelerates a trolley; the same force produces less acceleration on a larger mass. Remove the push and both continue at their own constant velocities. Zero net force permits rest or uniform motion.

Open the interactive experiment →

A moving trolley needs no continuing push.

நிகர விசை இல்லாதபோது பொருள் ஓய்விலோ சீரான வேகத்திலோ இருக்கும். நிறை அதிகமானால் ஒரே விசைக்கான முடுக்கம் குறையும்.

Key notes, relationships and model limits

Key relationship

a = Fnet/m; v = u + a min(t, τ). After τ, Fnet = 0 and v stays constant.

Remember

Common trap

A force is required to change velocity, not to maintain constant velocity on this ideal track.

Model limits

Horizontal frictionless track; equal constant forces applied for τ seconds; point masses; no collisions. The diagram rescales the common position axis.

What you will learn

Compare inertia and acceleration; distinguish motion from a change in motion.

Try the experiment

Play the equal-push preset. Scrub past the push duration. Then choose no force and vary both masses.

Think of it this way

An empty shopping trolley responds more quickly to a push than a loaded one.

Worked example

For F = 4 N, a 2 kg trolley has a = 2 m/s²; an 8 kg trolley has a = 0.5 m/s². From rest, a 2 s push gives velocities 4 and 1 m/s.

Why this matters

Real trolleys stop because friction supplies a net force. That does not contradict inertia.

Before you start

Vector components · velocity · SI units

Check your understanding

A trolley has velocity 2 m/s when its net force becomes zero. What follows?

It immediately stops
It continues at 2 m/s
It keeps accelerating

Read the explanation

Newton’s first law gives constant velocity when the net force is zero.

Course connection: CBSE XI Chapter 4; NEET/Main Unit 3; JEE Advanced Mechanics. Apply each exam’s stated assumptions.