Question

3. Mr. Hogan in his 3000 kg truck is driving down
highway 175 toward Crandall at 80 miles per hour
(36 m/s). He sees a police car up ahead and slows
down to 65 miles per hour (29 m/s). Determine the
magnitude of the impulse required to do this?
A. 46.2 kg.m/s
B. 429 kg.m/s
C. 2417 kg.m/s
D. 3724 kg.m/s
E. 21,000 kg.m/
seo Tool s

Answer 1

Answer:

$|I|=21,000\ kg.m/s$

Correct answer: Option E

Explanation:

Impulse and Momentum

The Impulse is defined as the change of momentum of an object in a certain interval. The formula is:

$I=\Delta p=p_f-p_o$

Where pf and po are the final and initial momentums respectively. Knowing that for m= mass of the object and v=velocity (or speed in the scalar form)

$p=m.v$

Thus

$I=m(v_f-v_o)$

Mr. Hogan's 3000 kg truck is initially at 36 m/s and later slows down to 29 m/s. We compute the impulse as follows

$I=3000\ kg(29\ m/s-36\ m/s)$

$I=3000(-7)\ kg.m/s$

$I=-21,000\ kg.m/s$

We are asked for the magnitude, thus

$|I|=21,000\ kg.m/s$

Correct Answer: Option E