4. Conjecture: Does thiction cause more energy to be wasted if the object is heavier? Why? Use the Gizmo to test this. Describe your results in your notebook or on a separate sheet.

3. Analyze: Friction causes work to be "wasted" as heat (which is why your hands get warm). A. Does friction waste more work on longer or shorter planes? B. How can you tell? C. Why do you think this is? [Hint: Remember the stick presses up on the item. Do your hands get warmer faster if you press them together harder as you rub?] Conjecture: Does friction cause more energy to be wasted if the object is heavier? Why? Use the Gizmo to test this. Describe your results in your notebook or on a separate sheet.

Which of the following sets of forces could not be in equilibrium? \( \begin{array}{ll}\text { (a) } 11,7,5 \text { newton. } & \text { (b) } 4,6,8 \text { newton. } \\ \text { (c) } 10,10,8 \text { newton. } & \text { (d) } 8,4,14 \text { newton. }\end{array} \)

The bullet hits the 50 cm thick wooden board with a speed of \( 108 \mathrm{~km} / \mathrm{h} \). What is the deceleration of the bullet, if it leaves the board after 3.5 s ?

3.- Calcula en joule la energía cinética traslacional que lleva una bala que tiene una masa de 7 gr si la magnitud de su velocidad es de \( 420 \mathrm{~m} / \mathrm{s} \). R 705.6 J

\( \left.\qquad R .3,6 \mathrm{~m} / \mathrm{s}^{2} ; 270 \mathrm{~m} / \mathrm{s}^{2} ; 1,6 \mathrm{~m} / \mathrm{s}^{2}\right] \) Determina l'accelerazione di gravita g' esercitata dalla Terra sulla Luna, sapendo che la distanza della Luna dalla Terra è 60,25 raggi terrestri e che l'accelerazione di gravità g è \( 9,8 \mathrm{~m} / \mathrm{s}^{2} \). [R. \( \left.0,27 \mathrm{~cm} / \mathrm{s}^{2}\right] \)