(i) Calculate the average acceleration of the coin.
(ii) If the mass of the coin is 8.5 g, what is the magnitude and direction of the average resultant force acting on it?
Explain, with the aid of a diagram, why the coin reaches a constant speed. (b) What is friction?
A cyclist exerts a constant force of 450 N causing the bicycle to accelerate at 4.8 m s2 until it reaches a velocity of 20 m s1 due west.
Given that the combined mass of the cyclist plus bicycle is 80 kg, calculate: (i) the net force (ii) the frictional force.
State two potential sources of the friction and a method of reducing each of them.
(10) (12) (6)
(12) (10)
CHAPTER CHECKLIST
FORMULAE: p mv
m1u1 m2u2 m1v1 m2v2 F ma
F Gm1m2 d2
W mg
g GM R2
Special case of Newton’s second law, derivation required at higher level only Newton’s law of universal gravitation
Weight Acceleration due to gravity, derivation required at higher level only
CONCEPTS: Unit for mass Definitions and units for momentum, force and weight Principle of conservation of momentum Newton’s three laws of motion F ma as a special case of Newton’s second law Newton’s law of universal gravitation Value of acceleration due to gravity on other bodies in space, e.g. Moon Variation of g, and hence W, with distance from centre of the Earth Friction: a force opposing motion
Momentum of a particle Principle of conservation of momentum (PCM)
