Question

select the correct answer.
an athlete is running at a constant velocity with a javelin held in his right hand. the force he is applying on the javelin to carry it is 5.0 newtons. if he covers a distance of 10 meters, what work has he done on the javelin?

a. 5.0 × 10¹ joules
b. 4.5 × 10¹ joules
c. -5.0 × 10¹ joules
d. 0 joules

Explanation:

Step1: Recall the work formula

The formula for work is \( W = F \cdot d \cdot \cos\theta \), where \( F \) is force, \( d \) is displacement, and \( \theta \) is the angle between force and displacement.

Step2: Analyze the angle

The athlete applies a force to hold the javelin (likely vertical, to counter gravity), while displacement is horizontal (running). So \( \theta = 90^\circ \), and \( \cos(90^\circ) = 0 \).

Step3: Calculate work

Substitute into the formula: \( W = 5.0 \, \text{N} \times 10 \, \text{m} \times \cos(90^\circ) \). Since \( \cos(90^\circ) = 0 \), \( W = 0 \, \text{joules} \).

Answer:

D. 0 joules