1. Three forces pull on a block, the first is 65 N and in the positive x directi
ID: 2124639 • Letter: 1
Question
1.
Three forces pull on a block, the first is 65 N and in the positive x direction. The second is 65 N in the negative x direction and the third is 45 N and is 90 degrees from the first two forces in the positive y direction. What can you say about the resultant force?
A) c. The resultant force is 45 N and in the negative y direction.
B) d. The resultant force is 65 N and in the negative y direction.
C) a. The resultant force is zero.
D) b. The resultant force is 45 N and in the positive y direction.
2.
A 7.93 kg box is pulled along a horizontal surface by a force FP of 84.0 N applied at a 47.0
Explanation / Answer
1) the two in the x directions cancels so answer is 45 in the positive y
so D)
2)
sum forces in the y:
84*sin(47) + N - 7.93*9.81=0
N=16.36 N
sum forces in the x
84*cos(47) - 0.35*16.36 = 7.93*a
a=6.5 m/s^2
3) Ei = E final
m gh = 1/2 mv^2
v = sqrt(2 gh) = sqrt(2*9.81*4.5)=9.4 m/s
4)
F - u N = ma
45-u*25*9.81 = 25*.75
u=0.107
so B)
5)
x = x0 + v0t + 1/2 a t^2 = 25*1.5 - 0.5*5*1.5^2=31.9
so A)
6) y direction
0 = 725 - 0.5*9.81*t^2
t=12.16 s
x direction
x = 655*12.16=7964 m
7) conservation of momentum
0.4*5.5E5 + 0.6*v = 0
v = 0.4*5.5E5/0.6=3.7E5
so B)
8)
a = G M /r^2 = 6.67E-11*5.98E24/(6371.0E3+250.0E3)^2=9.1
so A)
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