(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