Pulling an Object with a Force Meter – Weight, Friction and Spring Extension
Integrated ScienceForces & MotionAges 11–12Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Forces & Motion
A wooden block on a table is pulled by a spring force meter. Students drag the meter's hook (or the slider) to increase the pulling force: the spring stretches in proportion to the force and the pointer shows the reading; the block only starts to slide once the pulling force exceeds the maximum static friction. Change the mass to see the weight W = m·g and the friction increase with it; change the surface (ice, wood, concrete, rubber) to compare roughness; force arrows show the two forces balancing while the block stays still.
Lesson: Forces and Their Effects; Spring Extension; Measuring Force with a Force Meter; Weight and Mass; Friction
What it shows
A spring force meter works because the extension of its spring is proportional to the force on it (Hooke's law), so the scale can be marked in newtons. When the meter pulls a block that stays still, static friction grows to match the pull exactly, so the two forces are balanced and the block remains at rest. Only when the pull exceeds the maximum static friction, μ·W, does the block start to slide, and the sliding friction is then slightly smaller. The weight is W = m·g with g = 9.81 N/kg, so a heavier block or a rougher surface needs a bigger force to start moving.
How to use
Choose the Mass of the object and a Contact surface, then drag the meter's hook slowly to the right while watching the reading and the friction arrow. Note the largest force at which the block still does not move, then compare the four surfaces at the same mass and the same surface at different masses. Keep Show force arrows on so students see two equal and opposite forces while the block is at rest, and use Pause to read the values.
Parameters you can change
- Mass of the object 0.2–5 kg
- Contact surface Ice surface (very smooth), Wood surface, Concrete, Rubber mat (very rough)
- Initial pulling force 0–50 N
- Show force arrows
Questions to explore
- If you pull with 3 N and the block does not move, how large is the friction force acting on it?
- How does doubling the mass change the force needed to start the block sliding on wood?
- Which surface needs the smallest pull to start the block sliding, and what does this tell you about its coefficient of friction?
