A 1.00 -kg block is resting against a light, compressed spring at the bottom of a rough plane inclined at an angle of \(30.0^{\circ}\); the coefficient of kinetic friction between block and plane is \(\mu_{\mathrm{k}}=0.100 .\) Suppose the spring is compressed \(10.0 \mathrm{~cm}\) from its equilibrium length. The spring is then released, and the block separates from the spring and slides up the incline a distance of only \(2.00 \mathrm{~cm}\) beyond the spring's normal length before it stops. Determine a) the change in total mechanical energy of the system and b) the spring constant \(k\).

Short Answer

Expert verified
Based on the given problem, the change in total mechanical energy when the block slides up the incline is 0.1018 J, and the spring constant is approximately 97.24 N/m.

Step by step solution

01

Gravitational potential energy

Initially, the block is at the bottom of the incline, so its gravitational potential energy is 0 J.
02

Kinetic energy

Initially, the block is at rest, so its kinetic energy is also 0 J.
03

Elastic potential energy

Since the spring is compressed 10 cm (\(0.1\,\text{m}\)), its elastic potential energy is given by: $$E_s = \frac{1}{2}kx^2$$ The initial energy state of the system is: $$E_i = 0\,\text{J} + 0\,\text{J} + \frac{1}{2}k(0.1^2)$$ #Step 2: Calculate the final energy state of the system# When the block stops, it doesn't have any kinetic energy. We need to find the gravitational potential energy and the elastic potential energy of the spring.
04

Gravitational potential energy

The vertical height (h) at the stopping point is given by: $$h = (0.1 + 0.02) \sin{(30^\circ)} = 0.06\,\text{m}$$ So, the gravitational potential energy is: $$PE = mgh = (1.00\,\text{kg})(9.8\,\text{m/s}^2)(0.06\,\text{m}) = 0.588\,\text{J}$$
05

Elastic potential energy

At the stopping point, the spring is at its equilibrium length, so there is no elastic potential energy. The final energy state of the system is: $$E_f = 0.588\,\text{J} + 0\,\text{J}$$ #Step 3: Calculate the change in total mechanical energy# Using the work-energy theorem, we can write: $$ΔME = W_{f} = E_f - E_i = 0.588\,\text{J} - \frac{1}{2}k(0.1^2)$$ Now we need to find the work done against friction.
06

Find the work done against friction

The normal force (N) can be found using: $$N = mg\cos{30^\circ}$$ Now we can find the friction force (f) using the coefficient of kinetic friction: $$f = \mu_{k}N = (0.100)(1.00\,\text{kg})(9.8\,\text{m/s}^2)\cos{30^\circ} = 0.848\,\text{N}$$ The work done against friction is the product of the friction force and the distance the block slides: $$W_{f} = fd = 0.848\,\text{N} \cdot 0.12\,\text{m} = 0.1018\,\text{J}$$ We can now solve for ΔME: $$ΔME = 0.1018\,\text{J}$$ #Step 4: Calculate the spring constant# We can substitute the expression for ΔME into the work-energy theorem equation: $$0.1018\,\text{J} = 0.588\,\text{J} - \frac{1}{2}k(0.1^2)$$ Now we solve for k: $$k = \frac{0.588\,\text{J} - 0.1018\,\text{J}}{0.005\,\text{m}^2} = 97.24\,\text{N/m}$$ So, the spring constant is approximately 97.24 N/m, and the change in total mechanical energy of the system is 0.1018 J.

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