Um motorista dirigla seu carro de massa 1000 kg quando precisou acionar os freios para não provocar um acidente e atropelar um animal silvestre que atravessava a rodovia. O carro consegulu parar e deixou uma marca de pneu de 20 metros no asfalto. A força média que atuou no pneu no momento da freada fol de 10000 newtons. Considerando esses dados, determine: A. O trabalho realizado pela força de atrito. B. A velocidade do carro antes de íniciar a freada.

QUESTION 6 (Start on a new page.) It has been established that the planet Omega has a moon and that the moon of Omega orbits the planet at a height, above the surface of Omega, which is equal to twice the radius of Omega. The mass of planet Omega is \( 3 \times 10^{15} \mathrm{~kg} \) and the mass of its moon is \( 1.5 \times 10^{13} \mathrm{~kg} \). The radius of the planet Omega is \( 8.5 \times 10^{6} \mathrm{~m} \) and the radius of its moon is \( 2.5 \times 10^{5} \mathrm{~m} \). 6.1 Determine the distance between the centre of the planet Omega and the centre of its moon.

9. Si dejamos caer al suelo una piedra cuya masa es de 4 kg desde una altura de 4 m , ¿Cuál es la energía cinética cuando ya ha recorrido la mitad de la caída a) hacia el suelo? b) CCual es la velocidad cuando alcanza el suelo?

7.2 A beam of light travels from water to plastic. The speed of light in plastic is \( 2,05 \times 10^{8} \mathrm{~m} \cdot \mathrm{~s}^{-1} \). The refractive index of water is 1,33 . Calculate the refractive index of plastic.

3) Choose the correct alternative and rewrite the statement (i) The weight of a body on the earth's surface \( =\ldots \ldots . \). \( \begin{array}{llll}\text { (a) } \frac{G M m}{R} & \text { (b) } \frac{G M m}{R^{2}} & \text { (c) } G M m R^{2} & \text { (d) } \frac{G m}{R^{2}}\end{array} \)

QUESTION 7 (Start on a new page.) 7.1 Reflection of light (and other forms of electromagnetic radiation) occurs when the waves meet a surface or other boundary that does not absorb the energy of the radiation and reflects the waves off the surface. Draw a fully labelled ray diagram to illustrate reflection.