Question

A boat is cruising in a straight line at a constant speed of 2.5 m/s when it is shifted into neutral. After coasting 14 mm the engine is engaged again, and the boat resumes cruising at the reduced constant speed of 1.5 m/s. Assuming constant acceleration while coasting,

a. How much time did it take for the boat to coast the 12 m?
b. What was the boat’s acceleration while it was coasting?
c. What was the speed of the boat when it had coasted for 6.0 m? Explain.

Answer 1

Answer:

Explanation:

a ) distance s = 12 m .

constant speed = 1.5 m/s

time taken to coast 12 m

= distance / speed

= 12 / 1.5 = 8 s

b ) initial velocity u = 2.5 m /s

final velocity v = 1.5 m /s

displacement s = 14 m

acceleration a = ?

v² = u² + 2 as

1.5² = 2.5² + 2 a x 14

a = - .1428 m /s²

= - 14.28 cm / s²

c )

v = ?

u = 2.5 m /s

s = 6 m

a = -   .1428 m /s²

v² = u² - 2 as

= 2.5² - 2 x 6 x .1428

= 6.25 - 1.71

= 4.54

v = 2.13 m /s .