Fast Five Young's Modulus

A wire of circular cross-section, which obeys Hooke’s law, is used to suspend a basket as shown.

The Young modulus for the material of the wire is 2.5 x 10¹¹Pa.

When a weight of 34 N is added to the basket, the strain in the wire increases by 6.0 x 10^–5.

 

What is the radius of the wire? ^{9702/11/O/N/20#19}

• 7.2 x 10^–7 m

• 2.3 x 10^–6 m

• 8.5 x 10^–4 m

• 1.7 x 10^–3 m

1.      

An unstretched rubber cord is stretched by a force. The force F is plotted against the extension x. F is slowly increased from zero, causing the cord to extend along path P. F is then reduced back to zero along path Q.

 

What is represented by the shaded area?

• the elastic energy stored in the rubber cord

• the energy that causes plastic deformation

• the energy dissipated as heat

• the work done to extend the rubber cord

The graph shows the force–extension graph for a wire

 

The wire is already extended by a force of 60 ^{9702/12/O/N/20#21}

• 0.040 J

• 0.090 J

• 0.16 J

• 0.25 J

A tensile force of 7.00 MN is applied to a sample of steel. This causes the sample to extend by 5.00 mm in the direction of the force. The sample obeys Hooke’s law.

 

What is the work done to extend the sample? _{^{9702/13/O/N/20#21}}

• 17.5 J

• 35.0 J

• 17.5 kJ

• 35.0 kJ

A metal wire, of cross-sectional area A and unstretched length l, is subjected to stress s. As a result it has strain e. Which expression gives the Young modulus of the metal? ^{9702/11/O/N/21#19}

 

• 
• 
• 
• 

Three springs are arranged vertically as shown.

Springs P and Q are identical and each has spring constant k. Spring R has spring constant 3k.

What is the increase in the overall length of the arrangement when a force W is applied as shown?^{9702/12/O/N/21#22}

• 5W

  6k

• 4W

  3 k

• 7 kW

  2

• 4kW

A length of metal wire is attached to a fixed point and hangs vertically. Masses are then suspended from the wire. Assume that the cross-sectional area of the wire remains constant. A stress–strain graph for the wire is plotted, as shown.

What is represented by the shaded area under the graph?^{9702/12/O/N/21#22}

• Strain energy in the wire

• Strain energy in ___the wire___

  cross-sectional area of the wire

• Strain energy in ___the wire___

  Original length of the wire

• Strain energy in ___the wire___ original volume of the wire