(a) (i) Define force and state its S.I unit. (ii)... | WAEC SSCE - Physics - 2019 (Essay)

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(a) (i) Define force and state its S.I unit.
(ii) List the two types of solid friction.

(b) A car travelling at a constant speed of \(30\ \mathrm{ms}^{-1}\) for \(20\ \mathrm{s}\) was suddenly decelerated when the driver sighted a pot-hole. It took the driver \(6\ \mathrm{s}\) to get to the pot-hole with a reduced speed of \(18\ \mathrm{ms}^{-1}\). He maintained the steady speed for another \(10\ \mathrm{s}\) to cross the pot-hole. The brakes were then applied and the car came to rest \(5\ \mathrm{s}\) later.
(i) Draw the velocity-time graph for the journey.
(ii) Calculate the deceleration during the last \(5\ \mathrm{s}\) of the journey.
(iii) Calculate the total distance covered.

Answer

Part of journey	Area under graph	Distance (m)
\(0\) to \(20\) s	\(30\times20\)	\(600\)
\(20\) to \(26\) s	\(\frac{1}{2}(30+18)\times6\)	\(144\)
\(26\) to \(36\) s	\(18\times10\)	\(180\)
\(36\) to \(41\) s	\(\frac{1}{2}\times18\times5\)	\(45\)

Part of journey	Area under graph	Distance (m)
\(0\) to \(20\) s	\(30\times20\)	\(600\)
\(20\) to \(26\) s	\(\frac{1}{2}(30+18)\times6\)	\(144\)
\(26\) to \(36\) s	\(18\times10\)	\(180\)
\(36\) to \(41\) s	\(\frac{1}{2}\times18\times5\)	\(45\)

Friction

Motion

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(a) (i) Define force and state its S.I unit. (ii) List the two types of solid friction. (b) A car travelling at a constant speed of \(30\ \mathrm{ms}^{-1}\)...

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(a) (i) Define force and state its S.I unit. (ii) List the two types of solid friction. (b) A car travelling at a constant speed of \(30\ \mathrm{ms}^{-1}\)...

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