Q. A 12 kg runaway grocery cart runs into a spring with spring constant 210 N/m and compresses it by 70cm .What was the speed of the cart just before it hit the spring?

Q. Explain how you can lower the pitch of a note on a guitar by altering the thickness or the mass of the string. Why does a sounding board on a musical instrument produce louder sound? Would a plucked guitar string vibrate for a longer or a shorter time if the instrument had no sounding board? Why? Explain how you can lower the pitch of a note on a guitar by altering the length of the string.