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 ?

(a) (i) State the principle of superposition of waves. (ii) Distinguish between standing and stationary waves. (b) Define the following terms as applied to sound waves (i) Interference and beating. (ii) resonance and fundamental frequence.

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.

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 ?

2. For how long must a force of 10 N act on a body at rest of mass 400 grams for said body to reach a speed of \( 20 \mathrm{~m} / \mathrm{s} \) ?

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