Physics · Mechanical Properties Of Solids · NEET
No. Ultimate tensile strength (point D) is the maximum stress the material can take. The material does NOT break here. Beyond D, the curve goes down and the material finally breaks at the fracture point E, which is at a slightly lower stress. NEET loves this gap between D and E, so keep them separate.
After point D, the material gets a local thinning called a 'neck'. The area of cross-section shrinks a lot there, so even a smaller force produces enough stress to break it. Because stress on the graph is calculated using the ORIGINAL area, the plotted stress at fracture (E) looks lower than at D, even though the material is failing.
Look at how far point D (ultimate strength) and point E (fracture) are. If D and E are CLOSE, the material breaks almost right after its peak stress with little plastic stretch — it is brittle (like glass or cast iron). If D and E are FAR APART, the material stretches a lot before breaking — it is ductile (like copper or mild steel). This is the exact idea NEET 2019 tested.
No. Strength (how much stress before failing) and elasticity (how well it returns to shape / high Young's modulus) are different ideas. A material can have high ultimate strength but not be very elastic, or vice versa. Ultimate strength is about the fracture region; elasticity is about the linear region OA near the origin.
No. The yield point (B, also called the elastic limit) is where plastic deformation begins — the material stops returning to its original length. The ultimate tensile strength (D) is the highest stress on the whole curve, which comes AFTER the yield point. Order on the curve: O to A (elastic) to B (yield) to D (ultimate) to E (fracture).
The stress-strain curves are drawn for two different materials X and Y. It is observed that the ultimate strength point and the fracture point are close to each other for material X, but are far apart for material Y. We can say that materials X and Y are likely to be (respectively)
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the maximum stress (force per unit area) a material can bear before it starts to fail. On the stress-strain curve it is the highest point, marked D.
It is the point E on the stress-strain curve where the material actually breaks. It comes after the ultimate strength point D.
After point D the material forms a thin 'neck'. Since stress is plotted using the original area, the stress at breaking looks lower even though the material is failing there.
Brittle materials have D and E very close (break soon after peak stress). Ductile materials have D and E far apart (stretch a lot before breaking).
Brittle: glass, cast iron, ceramics. Ductile: copper, aluminium, mild steel — these can be drawn into wires because they stretch before breaking.
Not exactly. Ultimate strength is the maximum stress (at D). Breaking/fracture stress is measured at E. For brittle materials they are almost equal; for ductile materials the fracture value is noticeably lower.
