1) A mass of 1.0 kg is being lowered (directly downward) by a string at the rate
ID: 1482300 • Letter: 1
Question
1) A mass of 1.0 kg is being lowered (directly downward) by a string at the rate of 1.0 m/s2 such that the string is speeding up. Calculate the tension in the string.
A. 8.8 N B. 10.8 N C. 9.8 N D. 7.8 N E. 11.8 N
2)
If the mass were lowered 1.7 m, calculate the work done by the tension in the string.
A. 15 J
B. 18 J
C. -18 J
D. 19 J N
E. -15 J
3)
Calculate the change in the mass’ kinetic energy after the displacement of 1.7 m, assuming it started at rest.
A. 0.9 J
B. 1.7 J
C. 3.0 J
D. 6.0 J
E. 0 J
4)
If this net force in problem 3 acts for a time of 2.7 s, and the box was initially at rest, calculate the net work done during this time.
A. 111 J
B. 150 J
C. 39 J
D. 1500 J
E. 2220 J
Explanation / Answer
you commented that the answer for B) 15 N ,but this is wrong the answer is -15 N,you need include a minus sign
C) use work energy theorem
Work done by the net force = change in KE
Fnet *S = Kf-Ki
Ki = 0 J (since started from rest )
m*a*S = Kf
Kf = m*a*s = 1*1*1.7 = 1.7 J
So the answer is B) 1.7 J
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4) use v = u+ (a*t)
initiallyt at rest then u = 0 m/s
a = 1 m/s^2
t = 2.7 s
then final velocity is v = 0+(a*t) = 0+(1*2.7) = 2.7 m/s
net work done = change in KE = Kf-Ki = Kf = 0.5*m*v^2 = 0.5*1*2.7^2 = 3.645 J
i am getting 3.645 J but there is no options so once please check your options and let me know it
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