GED Science Practice Test: Energy, Forces and Chemistry

Speed is squared in the formula, so doubling v multiplies KE by 2² = 4. A factor of 2 would be correct only if kinetic energy were proportional to speed rather than to speed squared.

PE = 2 × 9.8 × 1.5 = 29.4 joules. The value 3.0 leaves out g, 19.6 leaves out the height, and 14.7 wrongly adds a factor of 12 that belongs in the kinetic energy formula.

Work = 300 × 4 = 1,200 joules, and power = 1,200 ÷ 6 = 200 watts. The value 1,200 is the work, not the power, and 50 divides the force by the time without using the distance.

By Newton's third law, when she pushes on the wall, the wall exerts an equal and opposite force on her, and that force accelerates her away. The two forces are always equal in size, so her push is not stronger than the wall's.

By Newton's first law (inertia), the passengers' bodies keep moving at the bus's earlier speed until a force such as a handrail or the floor stops them. No forward force acts on them; the bus slows down beneath them.

The forces point in opposite directions, so the net force is 30 − 12 = 18 newtons to the right, and a = 18 ÷ 6 = 3 m/s² to the right. Adding the forces gives 42 ÷ 6 = 7, and 18 is the net force, not the acceleration.

A battery stores chemical energy, which drives an electric current, and the bulb or LED converts that electrical energy into light (and some heat). The reverse order describes charging a battery with a solar cell, not using a flashlight.

Energy is conserved: the remaining 54 joules are not lost but are converted mainly into heat, which is why such bulbs get hot. The bulb is only 6 ÷ 60 = 10% efficient at producing light; energy is never destroyed.

Wavelength = speed ÷ frequency = 340 ÷ 680 = 0.5 meter. Dividing the frequency by the speed gives 2, which is the reciprocal of the correct answer.

Ultraviolet radiation has shorter wavelengths and more energy per photon than visible light, which is why it can cause sunburn and damage DNA. Infrared, microwaves and radio waves all carry less energy per photon than visible light.

Elements in the same group have the same number of outer (valence) electrons, so they react in similar ways; potassium, like sodium, is a reactive alkali metal. Elements in the same row, such as magnesium, have different numbers of valence electrons and different properties.

The mass number is the number of protons plus neutrons: 17 + 18 = 35. Electrons have very little mass and are not counted, so adding all three particles (52) is wrong, and 17 is the atomic number.

The left side has 2 nitrogen atoms and 6 hydrogen atoms; 2NH₃ also has 2 nitrogen and 2 × 3 = 6 hydrogen atoms, so the equation balances. A coefficient of 3 would give 3 nitrogen atoms on the right but only 2 on the left.

The pack feels cold because the dissolving process takes in thermal energy from your skin and the air, which makes it endothermic. "Cold" is not a form of energy that can be released or absorbed; only thermal energy moves, always from warmer to colder objects.

During a phase change, the added energy breaks the bonds holding the water molecules in the solid structure, so the temperature stays constant until all the ice has melted. Heat clearly enters the beaker, because the ice keeps melting.