Please answer 6-10 thank you

10) On a winter day a dad is giving his son a fun ride on a sled. Since there is no hill close by that is steep enough for downhill sledding, he actually pulls the sled behind him, running fast, so that despite the friction from the snow the sled reaches enough speed for the child to get excited. The initial speed of the sled is 1.5 m/s and the mass of the sled and child combined is 20 kg. If dad does 1800 J of work on the sled pulling it and friction does -2550 J of work on the sled, how fast is the sled after it was pulled down a vertical height of 4 m? H6) Ultrasound therapy might be used to relieve pain, as it deposits energy in deep tissue. The warming effect encourages healing by increasing metabolism at the cellular level. Ultrasound can effectively penetrate to a depth of about 200 wavelengths. In muscle, the speed of ultrasound is 1580 m/s. If you would like to penetrate muscle tissue to a depth of 3.0 cm, what frequency of ultrasound should you use? Calculate that frequency. Give your answer in Mega-Hertz. 7) A clarinet can be treated as a half-open pipe, where sounds are produced by standing pressure waves. a) For a clarinet of length 0.6 m, calculate the wavelengths of the first three harmonics. b) Draw the standing wave pattern (for displacement), that belongs to a wavelength of 0.80m. Assume the mouthpiece is on the left.8) Walking in a park your friend Dimitri is accidently hit by a stray golf ball from the neighboring golf course. The mass of the golf ball is 45 gram and it struck your friend's head with 31 m/s. Assume that the golf ball hits perpendicular to the surface of the head and bounces straight back with 24 m/s. If the golf ball was in contact with Dimitri's head for 2 ms (milli-seconds), what was the average net force during this blow? (Since you are now curious: For comparison, to fracture a skull the force needs to be greater than 4900 N, so your friend will most likely survive such an event.) 9) Ear damage from diving If the force on the ear drum increases by about 1.5 N above the force from the atmospheric pressure, the membrane can be damaged. When you go scuba diving in the ocean, below what depth could damage to your ear drum occur? Data: Diameter of ear drum 8.2 mm density of salt water: 1.03 x103 kg