Forces & Changing Shape
- For stationary objects, more than one force has to be applied to change their shape
- Their shape can change by:
- Stretching (forces in opposite directions away from the object)
- Bending (forces that distort the object)
- Compressing (forces in opposite directions towards the object)
- A combination of all three shape changes can also occur
Compression
- An example of compression is placing a mass on top of a spring placed on a flat surface
- The two forces are:
- The weight of the mass
- The reaction force from the surface to the spring
- These two forces are towards each other
The compression or stretching of a spring requires two forces
Stretching
- An example of stretching is placing a mass on the bottom of a vertically hanging spring
- The two forces are:
- The weight of the mass
- The tension in the spring
- These two forces are away from each other
Bending
- An example of bending is a diving board bending when a swimmer stands at the far end
- The two forces are:
- The weight of the swimmer
- The reaction force from the block to the dividing board
- These two forces act towards each other, but at different points on the object
- Bending can also be caused by two forces at an angle to each other
Forces on a diving board cause it to bend when a swimmer stands on one end
More than one force on an object can cause it to bend