7. Halfway through a cross country meet, a
runner's speed is 4 m/s. In the last stretch,
she increases her speed to 7 m/s. What is
her change in speed

3m/s

Explanation:

Data obtained from the question include:

Initial speed (s1) = 4 m/s

Final speed (S2) = 7m/s

Change in speed (ΔS)

ΔS = s2 — s1

ΔS = 7 — 4

ΔS = 3m/s

Therefore, the change in speed is 3m/s

the answer is d. matter from the air combined with the steel wool.