# Help with a physics question.

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#1
A pile driver, shown in the diagram, of mass 400 kg is allowed to fall from rest through a distance of 2 m on to a 300 kg concrete pile to drive it into the ground. Each impact drives the pile into the ground by a further 100 mm. (Assume acceleration due to gravity g=9.81m/s2).
Assuming that the pile driver remains in contact with the pile after impact and that momentum is conserved, use the principle of conservation of energy to calculate:

1. a. The kinetic energy of the driver and pile combination immediately after impact.
2. b. The change in potential energy of the driver and pile combination on moving into the ground.
3. c. The average ******ing force that brings the pile and driver to rest, ensuring use of the principle of conservation of energy.
4. d.Using D’Alembert’s principle, solve the same problem

5. e.Compare and contrast the use of the ‘principle of conservation of energy’ and ‘D’Alembert’s principle’ for solving this problem.

i think i know the answer to a, b and c i will post a picture of my working out. but i dont know how to go about answering question d i think i will get the same answers for kinetic and potential energy but i dont know how to work out the rest. Any help would be realy appreciated
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#2
updated working out
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1 year ago
#3
(Original post by didaw)
updated working out
For (a), you need to know that the driver and pile undergo inelastic collision NOT elastic collision.

For (c), you did not show that you are using conservation of energy.
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