1. Wht produces ccelertion? A orce 2. Wht is the reltionship between ccelertion nd ) mss inersely proportionl b) orce directly proportionl 3. I you he orce o riction, 30N, on n object, how much orce is needed to mintin constnt elocity? 30 N
4. I you hold 5N bll boe your hed, wht is the orce on the bll? Drw ree-body digrm nd explin. N = 5 N Net orce = 0N g = 5 N 5. Wht is the orce o the 5N bll when it is in ree ll (disregrding ir resistnce)? Drw ree-body digrm nd explin. Net orce = -5N g = 5 N 6. I n object is ccelerted by constnt orce o 15N nd encounters second orce o 15N in the opposite directions, wht hppens to the object? It continues t constnt elocity
7. I the orce cting on n object triples, wht hppens to the ccelertion? It triples 8. I the mss on n object triples, wht hppens to the ccelertion? It decreses by ctor o 3 (1/3) 9. Wht two things does the orce o riction bsiclly depend on? Types o surce (coeicient o riction) Norml orce 10. In which direction does riction ct? Opposite the motion
11. Explin terminl elocity. The point t which lling object stops ccelerting nd begins moing downwrd t constnt elocity. 12. When skydier hs reched terminl elocity, wht is the ir resistnce equl to? AR = g (Air resistnce = weight) 13. Wht is the skydier s ccelertion when he hs reched his terminl elocity? ccelertion = 0m/s 2 (constnt elocity)
14. Wht is Newton s second lw in words? In n eqution? The ccelertion is directly proportionl to the mgnitude o the orce in direction o orce, nd is inersely proportionl to the mss. = m 15. Discuss the orce when n object is t rest. = 0N 16. Discuss the orce when n object is moing t constnt elocity. = 0N 17. Discuss the orce when n object is ccelerting. > 0N in the direction o the motion. 18. Wht does the term d men? Wht is it equl to? orce down the hill; equl to x component o weight
19. Drw the ree body digrm when n object is ccelerting with no riction on lt surce? Wht is the orce equl to? N = g 20. Wht is the orce equl to when the object is ccelerting with riction on lt surce? = 21. Wht is the orce equl to when n object is ccelerting with no riction on n incline? = d 22. Wht is the orce equl to when the object is ccelerting with riction on n incline? = d
23. Why does it hurt to get jbbed with the pointy end o pencil, but not the erser end? Less re = more pressure Problems 1. An egg with mss o 9.6 g is ree lling rom tree. Neglecting ir resistnce, drw the ree-body digrm. 9.6g = 0.0096kg (0.0096kg)(-9.8m/s 2 ) g = 0.094N 2. A 20 kg crt is being pushed by 6 N orce t constnt elocity. Drw the ree-body digrm. N = 196 N = 6 N = 6N g = 196 N
3. A 2.0 N orce is pplied to 1.0 kg book to moe it cross rictionless desk. Wht is the book s ccelertion (neglecting riction)? N = 9.8 N 2.0N m g = 9.8 N = 2.0N m 1.0kg 2.0N 4. A rightwrd orce o 302 N is pplied to 28.6 kg crte to ccelerte it cross the loor. The coeicient o riction between the crte nd the loor is 0.750. Determine the ccelertion o the crte. N = 280 N 302N 302N = 302N g = 280 N m 28.6kg N 210N (1.0kg) 2.0m (0.75)(280N) 92N m 3.2m 2 2 (28.6kg) 302N 210N 92N
5. During ootbll workout, two linemen re pushing the coch on sled. The mss o the sled/coch is 300 kg. The coeicient o riction between the sled nd the grss is 0.8. The sled ccelertes t rte o 0.58 m/s2. Determine the orce pplied by the linemen. N = 2940 N g = 2940 N m 300kg 2 0.58m m (300kg)(0.58) 174N 174N 2352N 2526N N (0.8)(2940N) 2352N
6. A hockey plyer ccelertes puck (m = 0.167 kg) rom rest to 50 m/s in 0.0121 s. Determine the orce pplied by the stick to the puck. (Neglect riction) i t N = 1.6 N 50m 0m ( )(0.0121s) m 0.167kg 2 4132.2m g = 1.6 N m i 0m (0.167)(4132.2) 50m 690N d t 0.0121s
7. A sled rider with combined mss o 52.5 kg hs some initil elocity nd comes to rest due to rictionl orce o 3 N. I it tkes 23 seconds or the sled to stop, wht ws the initil elocity? = 3N N = 1.6 N g = 1.6 N 3 m 52. 5N kg i d i 0m t 23s 0m 3N (52.5)( ) 0.057m i m i t 1.3m i 2 ( 0.057)(23s)