Question

two cars with initial speed 2v and v, lock their brakes and skid to a stop. what is the ratio of the distance travelled

Answer 1

Answer:

4:1

Explanation:

Given that the initial speed of the first car, u = 2v while the initial speed of the second car, u = v. To find the distance travelled, we are going to apply one of the equations of motion. The equation chosen is

v² = u² - 2as, where

s = the distance needed

a = acceleration due to gravity

u = initial velocity which is v & 2v

v = final velocity which is 0

For the first car with initial velocity, 2v, on substituting into the equation, we have

v² = u² - 2as(1)

0 = 4v - 2as(1)

4v = 2as(1)

2v = as(1), making s(1) subject of formula we have

s(1) = 2v/a

Taking the second car, we have u = v

v² = u² - 2as(2)

0 = v - 2as(2)

v = 2as(2), making s(2) subject of formula, we have

s(2) = v/2a

Not, ratio of s1 : s2 =

2v/a : v/2a

s1/s2 = 2v/a ÷ v/2a

s1/s2 = 2v/a * 2a/v

s1/s2 = 4av/av

s1/s2 = 4/1

Therefore, the ratio of the first car to the second car is 4:1

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