1.At a certain instant, a 4.0-kg object is sliding eastward at a speed of 15 m/s
ID: 1268361 • Letter: 1
Question
1.At a certain instant, a 4.0-kg object is sliding eastward at a speed of 15 m/s, propelled by an eastward force of 35 N. The coefficient of kinetic friction between the object and the horizontal surface it slides on is 0.20. No other horizontal forces act on the object. Assuming all forces remain constant, determine how far the object travels in the next 3.0 s.
The object travels ...........m.
2. A box weighing 52 N slide across the floor. The floor exerts a friction force of 17 N on the box. What is the coefficient of kinetic friction between the floor and box?
The coefficient is...........
3. A 560 kg crate attached to a cable is rising upward and slowing down. The magnitude of its acceleration is 1.4 m/s^2. Determine the magnitude T of the tension in the cable.
The tension is T=..........N
Explanation / Answer
Number 1)
Net force = ma
35 - uFn = ma
35 - .2(4)(9.8) = 4a
a = 6.79 m/s2
Then apply d = vot + .5at2
d = 15(3) + (.5)(6.79)(3)2
d = 75.6 m
Number 2)
Ff = uFn
17 = u52
u = .327
Number 3)
Net force = ma
T - mg = ma
T - (560)(9.8) = (560)(-1.4)
T = 4704 N
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