(a) Give two examples each of: (i) rotational motion; (ii) linear motion. (b) Describe a laboratory experiment to determine the density of an irregularly shaped solid. (c) State Newton's second law of motion (d) Explain the term inertia. (e)
The diagram above illustrates a body of mass 5.0 kg being pulled by a horizontal force F. If the body accelerates at 2.0 ms\(^{-2}\) and experiences a frictional force of 5 N, calculate the: (i) net force on it; (ii) magnitude of F; (iii) coefficient of kinetic friction. [ g = 10 ms\(^{-2}\)]
Explanation
(a)(i) Rotational Motion; Examples: (1) Motion of a wind mill. (2) Motion of a turntable or disc. (3) Rotation of the earth about its axis. (4) Movement of the blade of an electric fan, etc.
(ii) Linear Motion; Examples are: (1) An athlete running on a straight track. (2) A car moving on a straight road. (3)A ball rolling on a level ground, etc.
(b) In the laboratory, the mass(m) of an irregular shaped solid can be determined using a chemical or beam balance using a graduated measuring cylinder fill it partially with water and the initial volume V\(_2\) recorded, then completely immersed the irregular solid shape in the water and the final volume V recorded. Volume of the solid = V\(_2\) - V\(_{1}\) But density = \(\frac{Mass}{ Volume}\) = \(\frac{M}{V_2 - V_1}\) (c) Newton's second law of motion states that the time rate of change of momentum of a body is directly propotional to the applied force acting on it and takes place in the direction of the force. (d) Inertia is the reluctance of a body to move if it is at rest or to stop if it is already in motion. The more the mass of a body, the greater is its inertia. (e)(i) Net force = F - F\(_1\) = Ma 5.0 x 2.0 = 10N (ii) F = Ma + F\(_1\) = 10 + 5 = 15.0N (iii) µ = \(\frac{F}{R} = \frac{F}{mg} = \frac{15}{5 \times 10}\) = 0.3
