Part A A traveler pulls on a suitcase strap at an angle 36° above the horizontal

Question

Part A

A traveler pulls on a suitcase strap at an angle 36° above the horizontal. If 257 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the strap?

Part B

A worker lifts a 20.0-kg bucket of concrete from the ground up to the top of a 25.0-m tall building. The bucket is initially at rest, but is traveling at 4.0 m/s when it reaches the top of the building. What is the minimum amount of work that the worker did in lifting the bucket?

A worker lifts a 20.0-kg bucket of concrete from the ground up to the top of a 25.0-m tall building. The bucket is initially at rest, but is traveling at 4.0 m/s when it reaches the top of the building. What is the minimum amount of work that the worker did in lifting the bucket?

Explanation / Answer

PART - A
Assuming Frictionless Surface.

Let the Tension in the strap = T
Then Horizontal Force = T*cos(36)

Work done = Force * Displacement
257 = T*cos(36) * 15
T = 257/(15*cos(36))
Tension in the Strap , T = 21 N

PART - B
Mass of bucket = 20.0 Kg
Height = 20 m

Initial K.E = 0
Final K.E = 1/2 * m*v^2
K.Efin = 1/2 * 20 * 4^2 = 160 J

P.E in = 0
P.E fin = m*g*h
PE fin = 20 * 9.8 * 25 J = 4900 J

Using Energy Conservation -
K.Ein + Work Done = K.Efin + P.Efin
0 + Work done = 160 + 4900
Work done = 5060 J

Work done = 5.07 kJ

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