Pesiapan Formatif Fisika Kelas 8 : Usaha Dan Energi + Pesawat Sederhana

Explanation
A telepon is a device that converts electrical energy into sound energy, allowing us to communicate through audio signals. When we speak into a telephone, our voice causes a diaphragm or a microphone to vibrate, which in turn converts the sound energy into electrical energy. This electrical energy is then transmitted through wires or wireless signals to another telephone, where it is converted back into sound energy, allowing the person on the other end to hear our voice. Therefore, a telephone is the correct answer as it converts electrical energy into sound energy.

Explanation
Air merupakan sumber energi yang dapat diperbaharui karena air dapat digunakan untuk menghasilkan energi listrik melalui pembangkit listrik tenaga air. Proses ini melibatkan penggunaan air yang menggerakkan turbin, yang kemudian menghasilkan energi mekanik yang diubah menjadi energi listrik. Selain itu, air juga dapat digunakan untuk menghasilkan energi panas melalui pemanasan air dengan tenaga matahari atau geothermal. Dalam kedua kasus ini, air dapat digunakan berulang kali dan tidak akan habis jika dikelola dengan baik.

Explanation
The correct answer is "potensial-kinetik-listrik." In a hydroelectric power plant, the energy transformation starts with the potential energy of the water stored in a reservoir. As the water falls from a higher to a lower level, this potential energy is converted into kinetic energy. The moving water then drives the turbines, which convert the kinetic energy into mechanical energy. Finally, the mechanical energy is transformed into electrical energy by the generator, producing electricity. Therefore, the correct order of energy transformation in a hydroelectric power plant is potential energy, kinetic energy, and then electrical energy.

Explanation
As the mango falls from the tree, its potential energy due to gravity decreases because it is moving further away from its initial position. At the same time, its kinetic energy increases because it is gaining speed as it falls. Therefore, the correct answer is "energi potensial gravitasi makin kecil, energi kinetik makin besar" which translates to "potential gravitational energy decreases, kinetic energy increases".

Explanation
The work done by a force can be calculated by multiplying the force applied by the distance over which it is applied. In this case, the force is 8 N and the distance is 5 meters. Therefore, the work done is 8 N * 5 m = 40 Joule.

Explanation
The work done by a force is equal to the product of the force and the displacement in the direction of the force. In this case, the force applied is 10 Newton and the displacement is 15 m/s for 10 seconds. Therefore, the work done is calculated as follows: Work = force x displacement = 10 N x 15 m/s x 10 s = 1500 Joule.

Explanation
The correct answer is 2500 Joule. The kinetic energy of an object is given by the formula KE = 1/2 * mass * velocity^2. In this case, the mass of the motor and the rider is 200 kg and the velocity is 5 m/s. Plugging these values into the formula, we get KE = 1/2 * 200 kg * (5 m/s)^2 = 1/2 * 200 kg * 25 m^2/s^2 = 2500 Joule. Therefore, the total kinetic energy of the motor and the rider is 2500 Joule.

Explanation
The potential energy of an object is given by the formula PE = mgh, where m is the mass, g is the acceleration due to gravity, and h is the height. In this case, the mass of the block is 5 kg, the acceleration due to gravity is 10 m/s^2, and the height is 7 meters. Plugging these values into the formula, we get PE = 5 kg * 10 m/s^2 * 7 m = 350 J. Therefore, the potential energy of the block is 350 Joules.

Explanation
A lever is a simple machine that helps lift heavy loads with less effort. It works based on the principle of torque, where the distance from the fulcrum (pivot point) affects the force required to lift the load. In this case, the lever is 4 meters long, with the fulcrum placed 2 meters away from the load. To balance the lever, the force applied on one side of the fulcrum must be equal to the force on the other side. Since the load weighs 200 Newtons, a force of 100 Newtons must be applied on the other side of the fulcrum to lift it. Therefore, the correct answer is 100 Newtons.

Explanation
The mechanical advantage (KM) of an inclined plane can be calculated using the formula KM = Length of inclined plane / Height of inclined plane. In this case, the length of the inclined plane is given as 4 meters and the height is given as 0.5 meters. Plugging these values into the formula, we get KM = 4 / 0.5 = 8. Therefore, the correct answer is 8.