Physics
Explain the following terms.
(a) Physical quantities
(b) Parallax error
(c) Beam balance
(d) Pendulum clock
(e) Thermometer
Answer
(a) Physical quantities — All the quantities that can be measured are known as physical quantities. Some examples of physical quantities are length, mass, area, time, temperature and volume.
(b) Parallax error — An error in measurement that arises due to wrong positioning of the eye is called parallax.
(c) Beam balance — A beam balance is a simple instrument to measure mass. It has a horizontal metallic beam supported at the centre with a pointer. Two equal pans hang from its ends. When both pans are empty or hold equal masses, the beam stays horizontal and the pointer vertical.
(d) Pendulum clock — A pendulum clock is a device that measures time using the principle of a simple pendulum. The pendulum swings at a regular rate, and this periodic motion is used to keep track of seconds and minutes.
(e) Thermometer — A thermometer is an instrument used to measure temperature. It consists of a thin glass capillary tube with a bulb at one end containing mercury. On contact with a hot body, the liquid expands and rises in the tube. The temperature is read from the calibrated scale in °C or °F.
Related Questions
Match the columns.
Column A Column B 1. A non-standard unit (a) Thickness of wire 2. Screw gauge (b) Square 3. Two-dimensional figure (c) Cubit 4. One century (d) Kink 5. Important part of a clinical thermometer (e) 100 years Give reasons for the following statements.
(a) A standard system of units was accepted.
(b) The correct position of eye is important to take measurements.
(c) A tailor uses measuring tape to take measurements.
(d) Jerks should be given to a clinical thermometer before using.
(e) Labs prefer using electronic balances.
Differentiate between fundamental quantities and derived quantities. Give examples if applicable.
Differentiate between standard units and non-standard units. Give examples if applicable.