Figure shows the force- extension graph for a wire that is stretched and then released. Force-extension graph for a wire. (a) Which point shows the limit of proportionality?

Proportionality limit is point on graph upto which the graph is a straight line (Hooke's law is followed) and force is directly proportional to extension. Therefore, point B shows limit of proportionality.

Figure shows the force- extension graph for a wire that is stretched and then released. Force-extension graph for a wire. (b) Which point shows the elastic limit ?

Elastic point is a point on force-extension graph from which stretched material can regain its original length. It lies beyond proportionality limit. Therefore in given graph point C is elastic limit.

Figure shows the force- extension graphs for four springs, A, B, C and D. Force-extension graphs for four different springs. (a) State which spring has the greatest value of force constant.

F = - k x where F is force , k is force constant and x is extension or compression. Since spring D undergoes the least extension therefore, it has the greatest value of force constant.

Figure shows the force- extension graphs for four springs, A, B, C and D. Force-extension graphs for four different springs. (b) State which is the least stiff.

According to Hooke's law F = - k x where F is force , k is force (spring) constant and x is extension or compression. Also, that spring A has the greatest extension therefore, spring A is least stiff.

Figure shows the force- extension graphs for four springs, A, B, C and D. Force-extension graphs for four different springs. (c) State which of the four springs does not obey Hooke's law.

∵ F = - k x Therefore, force extension graph of spring which obey Hooke's law must be a straight line. So we can conclude from the graph that spring A and C do not obey Hooke's law for given range of force.

EASY

AS and A Level

IMPORTANT

Earn 100

(a) Why is it difficult to hold an inflated plastic ball underwater?

Important Questions on Matter and Materials

EASY

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 7 - Matter and Materials>Questions>Q 7

(b) A submarine floats at rest under the water. To rise to the surface compressed air is used to push water out of its 'ballast' tanks into the sea. Why does this cause the submarine to rise?