Question

Calculate the Impulse necessary to stop a
travelling at 72 kmph.
2000kg car​

Answer 1

Answer:

Explanation:

Given :

• Initial velocity (u) = 72 km/h
• Final velocity (v) = 0 km/h
• Mass of a car (m) = 2000 kg

To Find :

• Impulse, J.

Formula to be used :

• J = Δp

Here,

• J = impulse
• Δp = Change in momentum

Solution :

★ Converting units,

Initial velocity = 72 km/h

⇒ v = 72 × 5/18

⇒ v = 20 m/s

Final velocity = 0 km/h

⇒ v = 0 × 5/18

⇒ v = 0 m/s

★ Impulse,

J = Δp

.°. J = m(v - u)

⇒ J = 2000(0 - 20)

⇒ J = 2000 × -20

⇒ J = -40000 N-S

Hence, Impulse is -40000 N-S.

Answer 2

${\bold{\sf{\underline{Understanding \: the \: question}}}}$

✵ This question says that there is a car of mass 2000 kg. It's travelling at speed of 72 km/h. Now it says that we have to calculate the impulse necessary to stop the car.

${\bold{\sf{\underline{Given \: that}}}}$

❈ Mass = 2000 kg

❈ Speed ( Final velocity ) = 0 km/h

❈ Initial velocity = 72 km/h

Note : The final velocity be 0 because there is a brake that time means when an object is on rest the it's velocity be 0 by itself.

${\bold{\sf{\underline{To \: find}}}}$

❈ Impulse necessary to stop the car.

${\bold{\sf{\underline{Solution}}}}$

❈ Impulse necessary to stop the car = - 40000 N-S

${\bold{\sf{\underline{Using \: concept}}}}$

❈ Finding impulse formula.

${\bold{\sf{\underline{Using \: formula}}}}$

❈ Impulse = ∆p

${\bold{\sf{\underline{We \: also \: denote \: these \: as}}}}$

✵ ∆p means Momentum change.

✵ Impulse also denote as J.

✵ Mass as m

✵ Final velocity as v

✵ Initial velocity as u

${\bold{\sf{\underline{Some \: procedure}}}}$

❈ To solve this question we have to use the formula to find Impulse. But there is a twist and it's the velocities are in km/h and as we know that we have to convert them in m/s So (conventing them) noe we get these in m/s easily. Now, using formula but we have to put v , u or else in this formula. ( putting the values ) we get our final result very easily! And the final result is 40000N-S.

${\bold{\sf{\underline{Full \: solution}}}}$

☃ Convertation of km/h into m/s

~ Final velocity

➝ Final velocity = 72 × ${\bold{\sf{\dfrac{5}{18}}}}$

➝ Final velocity = 4 × 5

➝ Final velocity = 20 m/s

~ Initial velocity

➝ Initial velocity = 0 × ${\bold{\sf{\dfrac{5}{18}}}}$

➝ Initial velocity = 0 m/s

☃ Finding impulse

➝ Impulse = ∆p

➝ Impulse = m(v-u)

➝ Impulse = 2000(0-20)

➝ Impulse = 2000(-20)

➝ Impulse = 2000 × -20

➝ Impulse = -40000 N-S

• Therefore, Impulse = -40000 N-S