Question

1. an object of mass 5.0 kg is lifted vertically upward by 2.0 m. assuming the acceleration due to gravity is 9.8 m/s², how much work is done against gravity?

a. 10 j b. 20 j
c. 49 j d. 98 j

Explanation:

Step1: 计算物体重力

$G = mg = 5.0\ \text{kg} \times 9.8\ \text{m/s}^2 = 49\ \text{N}$

Step2: 计算克服重力做功

$W = Gh = 49\ \text{N} \times 2.0\ \text{m} = 98\ \text{J}$

Answer:

D. 98 J