Newton’s Second Law Demonstration Apparatus

Quick Answer: The Newton’s Second Law Demonstration Apparatus is a mechanics set-up for showing that acceleration equals net force divided by mass, F = ma. As pictured, weights hung over a pulley pull a moving part along an arm whose angle can be set, so students change the force or the mass and measure the effect on acceleration.

Testing F = ma in Class

The listing image of the Newton’s second law demonstration apparatus shows an inclined arm on a base with angle markings, a pulley at the upper end and a hanger for added weights, with labels for force in newtons and acceleration in metres per second squared. Adding weights to the hanger increases the pulling force, and changing the arm angle changes how much of the moving part’s own weight acts along the slope, so students can vary the net force in two ways.

Newton’s second law says that the acceleration of an object is proportional to the net force on it and inversely proportional to its mass. Two classic experiments follow. Keep the total moving mass constant and increase the force by transferring weights from the moving part to the hanger; the acceleration should rise in proportion. Then keep the force fixed and add mass to the moving part; the acceleration should fall. Plotting acceleration against force gives a straight line through the origin whose gradient is one over the mass.

Friction is the main source of error, and the adjustable angle helps here: tilting the arm until the moving part just keeps going at a steady speed after a push balances friction with a component of gravity. Acceleration can then be found from the distance travelled and the time taken, using s = ½at² from rest, or with a motion sensor or video analysis. The weights, timer and any sensors supplied should be confirmed with the order.

Specifications

Applications

• Verifying that acceleration is proportional to net force at constant mass
• Showing that acceleration falls as mass increases at constant force
• Compensating for friction with a slight incline
• Resolving the weight of an object on an inclined plane
• Graphing results to find mass from the gradient

Care & Handling

• Keep the pulley clean and check that it turns freely; a sticky pulley adds friction that spoils the results.
• Place a soft stop at the end of travel so the moving part and falling weights are not damaged.
• Use thread strong enough for the heaviest load and replace frayed thread at once.
• Lock the angle adjustment before each run so it cannot slip.

Why Choose LabEquip

Physics teachers at secondary and pre-university level usually buy this as core mechanics lab equipment for the laws of motion practical. LabEquip lists it in the STEM kits range with the Gravity Demonstration Tower, which covers free fall before force and acceleration are linked. Send your requirements through the contact page.

Frequently Asked Questions

What does Newton’s second law state?

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In equation form, F = ma, with force in newtons, mass in kilograms and acceleration in metres per second squared.

Why move weights from the moving part to the hanger instead of adding new ones?

Adding new weights would change both the force and the total mass being accelerated. Moving weights from the moving part to the hanger increases the pulling force while keeping the total mass constant, so only one variable changes.

How can friction be reduced in the experiment?

Tilt the track slightly so that, after a gentle push, the moving part travels at constant speed. The small component of its weight down the slope then balances friction, and any extra acceleration comes from the hanging weights.

How is acceleration measured?

Release the moving part from rest, measure the distance it travels and the time taken, and calculate the acceleration as twice the distance divided by the time squared. Light gates, a motion sensor or slow-motion video give more accurate times than a stopwatch.

What graph should students plot?

Plot acceleration against force at constant mass; it should be a straight line through the origin, and the gradient equals one divided by the total mass. A second graph of acceleration against one divided by mass, at constant force, is also a straight line.

What is one newton?

One newton is the force that gives a mass of one kilogram an acceleration of one metre per second squared. It is roughly the weight of a small apple on Earth.

Last Updated: September 2026