A variable is directly proportional to another if it doubles or triples when the other one does the same.

The stretch of a spring that returns to its original shape when the stretching force is removed.

The stretch of a spring as it is permanently stretched out of shape.

A measure of how stiff a spring is and how hard it is to stretch or compress.

For elastic deformations, extension (or compression) is directly proportional to the force applied.

Stretching a spring analysis (F=ke)

Physics

In the Forces make things change unit, they will build on this knowledge to learn how to combine forces in two dimensions, how to calculate acceleration from a resultant force and how to calculate forces in collisions and explosions.

In the Measuring and calculating motion unit, pupils learnt how to measure and calculate velocity and acceleration, and how to interpret displacement-time and velocity-time graphs. 

Energy of moving objects

When one variable doubles, the other variable doubles.

When one variable increases by 10, the other variable increases by 10.

When one variable becomes 5 times greater, the other becomes 5 times greater.

When one variable halves, the other variable halves.

If two variables are directly proportional, which of the following statements are correct?

All springs have the same spring constant.

Stiffer springs have higher spring constants.

Stiffer springs have lower spring constants.

Which of the following statements about the spring constant is correct?

Each of the following graphs shows extension against force for three springs. The scales are the same on all of the graphs. Which graph represents the spring with the smallest spring constant?

For elastic deformation, extension (or compression) is directly proportional to the force applied. 
What is the name of this law, and how is it expressed as an equation?

Cars have stiff suspension springs to ensure a smoother ride. If the spring constant of one of these springs is 60,000 N/m, the force needed to compress the spring by 2.0 cm is {{}} N.

A spring has an unstretched length of 0.6 m. When a force of 200 N is applied, it stretches to a length of 1.0 m. 
What is the spring constant of the spring?

Which of the following is the unit of force?

An object is stretched by a force, but returns to its original shape when the force is removed. This type of deformation is called {{}} deformation.

An object is stretched by a force and does not return to its original shape when the force is removed. This type of deformation is called {{}} deformation.

The difference between the stretched and unstretched lengths.

Which of the following describes the extension of a spring?

Which of the following describes a variable in an experiment?

Rearrange the formula a = b ÷ c to make b the subject.

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