A child does 350 J of work while pulling a box from the ground up to his tree ho

Question

A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is 4.0 m above the ground. What is the mass of the box?        A) 5.3 kg
       B) 6.7 kg
       C) 8.0 kg
       D) 8.9 kg
       E) 87.5 kg Question 3.You carry a 7.0 kg bag of groceries 1.2 m above the ground at constant velocity across a 2.7 m room. How much work do you do on the bag in the process?        A) 0.0 J
       B) 82 J
       C) 185 J
       D) 157 J
       E) 23 J A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is 4.0 m above the ground. What is the mass of the box?        A) 5.3 kg
       B) 6.7 kg
       C) 8.0 kg
       D) 8.9 kg
       E) 87.5 kg

Explanation / Answer

1st question:
Work done = potential energy change
350 = m*g*h
350 = m*9.8*4
m = 8.9 Kg
Answer: D

2nd question:
Since we arecarrying grocerries at constant velocity throughout the room.
There is no chnage in kinetic energy or potential energy. So work done will be 0
Answer A

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