Test 2 completed Flashcards
Why is there no resultant force?
opposite forces are equal in magnitude
What is specific heat capacity?
The energy required PER unit mass PER unit temperature increase.
What is internal energy
A measure of the total energy of all the particles in an object.
Several ice cubes are at a temperature of 0°C. The ice cubes are dropped into the water and
the internal energy of the water decreases.
(i) Give a simple molecular account of this decrease in internal energy.
Internal energy depends on kinetic energy of molecules. Kinetic energy decreases.
As the temperature of the water decreases, some of the ice melts.
(i) Explain why this ice melts.
Kinetic energy of the ice is absorbed by the water. This energy is used to break bonds between ice molecules.
Define work done.
Energy transferred by a force when it moves.
Define principal focus
the point at which the rays of light, parallel to the principal axis converge after passing through the converging lens.
Define focal length
The distance from the centre of the lens to the principal focus.
Medical use of X-rays
For X-ray shadowgraphs. Absorbed by bones. Shadow is produced by bones.
Describe, in terms of particles, how the rod becomes negatively charged when rubbed with
the cloth.
Friction causes the electrons of the cloth to move from the cloth to the rod. The cloth is now positively charged and the rod is negatively charged.
Explain why the ball jumps up to the negatively charged rod.
The ball has a positive charge because its electrons have repelled to the earth. Opposite charges attract.
Define current
Current is the rate at which electric charge passes a point in a circuit.
The brightness of the light that is incident on the LDR increases.
Explain what happens to the potential difference (p.d.) across the 450Ω resistor. (two resistors parallel each other including the 450 one)
Resistance of the LDR decreases. Current in the circuit increases.
p.d of the 450 one decreases.
p.d of the other resistor increases. (more p.d because other has less p.d)
Describe the composition and structure of a neutral atom of uranium‐235.
Very small nucleus surrounded by electrons in the orbit. This many protons=the same number of electrons. This many neutrons.
What is temperature?
a measure of the average energy of the particles in a substance
