Question

9(a). Define each of the following terms as used with simple machines: (i) pivot; (ii) load; (iii) efficiency.
9(b). A truck of mass 1.2×10³ kg is pulled from rest by a constant horizontal force of 25.2 N on a levelled road. If the process is 60 km h⁻¹, calculate: (i) work done by the force; (ii) distance travelled by the truck in reaching the maximum speed.
9(c). State two differences between absolute zero temperature and ice point.

Accepted Answer

(a)(i) Pivot is the point about which turning effect occurs in a machine.
(ii) Load is the force overcarried by effort.
(iii) Efficiency of a machine is the ratio of work/energy output to the work or energy input, expressed as a percentage.
(b)(i) v=60kmh⁻¹=16.67ms⁻¹. Work done by the force=change in kinetic energy=½mv²=½×1.2×10³×16.67²=1.67×10⁵ J.
(ii) Distance travelled = W/F = 1.67×10⁵/25.2 ≈6630 m = 6.63 km.
(c) Differences: Absolute zero is the temperature at which all molecules are at rest, has a value of 0K/-273.15°C, and is not a fixed point on the Celsius scale. Ice point is the temperature at which vibratory motion still occurs, has a value of 0°C/273.15°C on the absolute scale, and is a fixed lower point on the Celsius scale.

WAEC Physics 2023 Theory — Question 9

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