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SECTION B : DYNAMICS
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3.
(a)
i. In one or two sentences, summarise the Principle of Work and Energy. (3 marks)
A spring hammer is shown in Fig. 3a. The hammer has a mass of 40 kg, and is released at
position 1 from rest. At position 2 the hammer strikes a work piece, and the two light springs
(each having a spring constant of k =8 kN m-1) are unextended. Calculate:
ii. the weight potential energy of the hammer at position 1 (take position 2 as a datum for
measuring elevation); (2 marks)
iii. the total spring potential energy at position 1; (4 marks)
iv. the kinetic energy and speed of the hammer at position 2 (assume that there are no non-
conservative forces and that the springs have negligible mass) (3 marks)
v. Write down a generic expression of the Principle of Work and Energy that relates
potential energy, kinetic energy and work done by non-conservative forces (2 marks)
vi. If the same hammer as in Fig. B1 hits the work piece at a speed of 3.6 m/s, what has been
the total work done by non-conservative forces between position 1 and 2? (3 marks)
Fig. 3a: Schematic of a spring hammer.
Question 3 Continued Overleaf
5
SECTION B : DYNAMICS
____________________________________________________________________
3.
(a)
i. In one or two sentences, summarise the Principle of Work and Energy. (3 marks)
A spring hammer is shown in Fig. 3a. The hammer has a mass of 40 kg, and is released at
position 1 from rest. At position 2 the hammer strikes a work piece, and the two light springs
(each having a spring constant of k =8 kN m-1) are unextended. Calculate:
ii. the weight potential energy of the hammer at position 1 (take position 2 as a datum for
measuring elevation); (2 marks)
iii. the total spring potential energy at position 1; (4 marks)
iv. the kinetic energy and speed of the hammer at position 2 (assume that there are no non-
conservative forces and that the springs have negligible mass) (3 marks)
v. Write down a generic expression of the Principle of Work and Energy that relates
potential energy, kinetic energy and work done by non-conservative forces (2 marks)
vi. If the same hammer as in Fig. B1 hits the work piece at a speed of 3.6 m/s, what has been
the total work done by non-conservative forces between position 1 and 2? (3 marks)
Fig. 3a: Schematic of a spring hammer.
Question 3 Continued Overleaf
5
