# Physics Question

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#1
I have a question, which I am unsure I have worked it out properly. Could someone please help. The question is:

The spring has a spring (force) constant of 80Nm-1. The energy stored in the spring is used to propel a dart of a mass of 40g. The spring is compressed by 6.0cm and then released.
i) How much energy is stored in the spring when its compressed by 6.0cm?
ii) Calculate the speed of the dart, assuming 50% of the energy stored by the spring is transferred as kinetic energy of the dart.
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4 years ago
#2
(Original post by flightlesss)
I have a question, which I am unsure I have worked it out properly. Could someone please help. The question is:

The spring has a spring (force) constant of 80Nm-1. The energy stored in the spring is used to propel a dart of a mass of 40g. The spring is compressed by 6.0cm and then released.
i) How much energy is stored in the spring when its compressed by 6.0cm?
ii) Calculate the speed of the dart, assuming 50% of the energy stored by the spring is transferred as kinetic energy of the dart.
First make sure to convert everything into the correct units. So 6.0cm = 0.06m.
Then 40g into 0.04kg.

Part a)

Using E = 0.5F△L. I took F=k△L and made the energy equation 0.5k△L^2.

Inserting values 0.5 x 80 x 0.06^2 = 0.144J. I then rounded to 0.14J as everything is in 2d.p.

b)

50% of 0.144J is 0.072J.

E = 0.5mv^2

sqrt(2E/m) = v

sqrt(2x0.072/0.04) = 1.9ms^-1.
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