Summary OCR A level Physics A 3.4 Materials

3.4 Materials

, and Hooke 's Law
Springs

change the shape of an object you
To
,
need a
pair
of equal and opposite forces .




> > <

tensile forces compressive forces
Hooke's law : the extension of a
spring
is
directly
proportional to the force applied , up until
the elastic limit .




Force extension
graph
-

:



F
from the origin to A extension ,

A. is
directly proportional to

force applied and the
spring
only deforms elastically (will
return to
original shape /
Point A is the elastic limit From
.




here onwards,
deformation
is
plastic
.




0 x
;

f- Roc F, N
-




force ,
in newtons ,


per metre Nm
"
K, force constant ,
in newtons ,


X, extension ,
in metres , m .




The larger the
force constant ,
the stiffer the
spring .




x can also represent the compression of the spring .