Work Power & Mechanical Advantage

Answers to worksheet given on Friday October 3

1. Easy question: just divide the work by the time
   ANS: 46 N
2. Various answers but a ramp trades distance for force. Remember that the work or energy is conserved so push the object a further distance requires less effort
3. Find F_g 12 x 9.8 = 117.6 N.
   Divide this value by 4 (the MA)
   ANS: 29.4 N
4. Make sure you sketch a diagram F_net horizontal 55.3 x cos 35^o = 45.3 N
   F_m = F_net + F_friction = 50.9 N
   F_pull = F_m divided by cos 35^o
   ANS: 62.1 N
5. Using F = ma, F = 40.8 N (120 x 0.34)
   Using W = Fd, 40.8 x 3
   ANS: 122.4 J
6. a) Work to lift = mgh 45 x 9.8 x 2.5
       ANS: 1102.5 J or 1.10 x 10³J
   b) IMA = ramp distance divided by lift distance 7.5/2.5
       ANS: 3
   c) MA = load divided by effort. The load is 45 x 9.8 = 441 N. The effort is ? N. The MA is 3. Therefore effort is load divided by MA
       ANS: 147 N
7. Diagram required with the ratio of effort distance to load distance 4:1
8. Is yours, no excuses, think and do a bit of research
9. List the data first; P = 400 W, t = 14 s, d = 2.0 m
   Three equations to use P = W/t to find work (W), then W = Fd to find force (F) then F = ma to find mass (m) remember that a = g = 9.8 m/s²
   ANS: 285.7 kg ( big industrial door).