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# Materials and solids watch

1. How should I work out this question?

Q)
Energy stored per unit mass (Jkg^-1)

Modem spring steel - 130
Tendon in leg - 2500
Rubber cord. - 8000

Show that a car of mass 1200kg would need steel springs of total mass approximately equal to 3kg to store energy when it encounters pot-holes of depth 3 cm
(3 marks)

I appreciate all solutions and suggestions a lot!
2. (Original post by Iluv2edgedsword)
How should I work out this question?

Q)
Energy stored per unit mass (Jkg^-1)

Modem spring steel - 130
Tendon in leg - 2500
Rubber cord. - 8000

Show that a car of mass 1200kg would need steel springs of total mass approximately equal to 3kg to store energy when it encounters pot-holes of depth 3 cm
(3 marks)

I appreciate all solutions and suggestions a lot!
Hi there, so you need to think about the change in potential energy when the car drops 3 cm
So as you know the potential energy change will be
Thus the spring needs to absorb 360 J worth of energy.
This is equivalent to 360/130= 2.76 kg which is about 3, I guess
3. (Original post by langlitz)
Hi there, so you need to think about the change in potential energy when the car drops 3 cm
So as you know the potential energy change will be
Thus the spring needs to absorb 360 J worth of energy.
This is equivalent to 360/130= 2.76 kg which is about 3, I guess
Grateful for thine help!

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