1. Vectors
Day 4
Lyzinski Physics

2. Vectors Problem Packet Homework Solutions
(19-23)

3. In conclusion, the cake will travel South 51.5o West.
19. Two ants at a picnic find a small piece of cake. Each picks up the cake and tries to carry it home. The first ant’s home is at a bearing of [W 15o N] and he pulls with a force of 10 dynes. The second ant’s home is at a bearing of [S 15o W] , and he pulls with a force of 13.5 dynes. What do you predict will happen? In which direction will the cake travel?
x-components:
10 dynes
15o
(-3.49) = dynes
2.59
y-components:
9.66
15o
(-13.04) = dynes
In conclusion, the cake will travel South 51.5o West.
13.5 dynes
13.04
16.8 dynes
51.5o
10.45
3.49
13.15

4. 20. Linda is pulling a sled with a force of 20 pounds and is heading on a bearing of N30E. Elaine begins to pull the sled with a force of 15 pounds on a bearing of N5W. What force is exerted on the sled and in which direction does it go?
32.26
8.69
1.31 10
17.32
14.94
15 lbs
20 lbs 5o
33.4 lbs
15.1o
30o
x-components:
= 8.69 lbs
y-components:
= lbs

5. + = 21. Find the resultant of a 120-Newton force North and an
80 Newton force at N45 E.
56.57
120 N + =
185 N
56.57
45o
80 N
176.57
x-components:
= N
72o
56.57
y-components:
= N

6. 22. Two water skiers are being pulled by a boat
22. Two water skiers are being pulled by a boat. The first skier exerts a force of 300 pounds North on the boat; the second skier exerts a force of 400 pounds at N75 E. Find the resultant of the two forces.
386.37 =
300 lbs +
103.53
75o
386.37
400 lbs
403.53
558.7 lbs
43.8o
x-components:
= lbs
y-components: =

7. 23. Three brothers are playing at the local playground with a frisbee
23. Three brothers are playing at the local playground with a frisbee. Each grabs it at the same time. Robbie grabs it at the N63 E point and exerts a force of 100 pounds on it. Chip grabs it at the N27 W point and exerts a force of 100 pounds on it. Ernie pulls with pounds at the S18 W point. Who gets control of the frisbee?
45.399
100 lbs
141.4 lbs
89.101
89.101
27o
63o
18o
45.399
x-components:
( ) = 0
y-components:
( ) = 0
Since both sets of components are zero, NOBODY wins (the frisbee doesn’t even move)
43.695

8. Vectors Problem’s from Buffa book (pp. 95-96)

9. Day #4

10. has balanced forces acting on it
zero

11. 375 lb
649.5 lb
Notice that for equilibrium problems (where nothing is moving), the components always sum up to zero.
750 lb
Fpole W x: y:
F = 0  F = -375 lb or F = 375 lb 
649.5 – W =  W = lb

12. N
51.30 N
150 N N
51.30 N
70o W x: y:
– = 0  DUH!
– W = 0  W = N

13. Solve simultaneous equations!
T2sin60
T2cos60 T2 T1
T1cos60
T1sin60 x: y:
T2sin60 - T1cos60 = 0
T1sin60 + T2cos = 0
50 N
Solve simultaneous equations!
T2sin60 - T1cos60 =  T2 = (T1cos60)/sin60 = T1
T1sin60 + T2cos =  T1sin60 + (.577T1)cos = 0
1.155T1- 50 =  T1 = 43.3 N
T2 = .577T1  T2 = N

14. F = (3 x + 4 y ) N notation F = (3 x + 4 y ) N notation ^ OR Fy = 4N
Fx = 3N
Fy = 4N

15. “Day #4 Vectors HW Problems” (from the packet, #’s 24-25)
Tonight’s HW
“Day #4 Vectors HW Problems” (from the packet, #’s 24-25)
Do Buffa, pp , problems 17, 30, 44, 45