Question

A car is travelling at a speed of 90km/h brakes are applied so as to produce a uniform acceleration of -0.5 m/s2. Find how far will the car go before it is brought to rest

Answer 1

GIVEn

A car is travelling at a speed of 90km/h brakes are applied so as to produce a uniform acceleration of -0.5 m/s2.

TO FINd

Find how far will the car go before it is brought to rest

SOLUTIOn

• Initial velocity (u) = 90km/h
• Final velocity (v) = 0
• Acceleration (a) = - 0.5 m/s²
• Distance (s) = ?

→ u = 90km/h

→ u = 90 × 5/18

→ u = 25 m/s

Apply this formula

→ v² = u² + 2as

→ (0)² = (25)² + 2*(-0.5)*s

→ 0 = 625 - s

→ s = 625 m

Hence, distance travelled by car is 625m before it comes in rest

_____________________

NOTE :

Minus(-) shows retardation

Answer 2

$\bf{\orange{\underline{\bf{Given}}}}$

• Initial velocity (u) = 90 km/h. 90×5/18 = 25 m/s. --- ( car is moving )

• Final Velocity (v) = 0 m/s (Car Brought to be at rest)

• Acceleration (a) = -0.5 m/s² (Retardation)

$\bf{\orange{\underline{\bf{ToFind}}}}$

• Distance travelled (s)

$\bf{\orange{\underline{\bf{Solution}}}}$

By using the third equation of motion, we get,

• ➤ 2as = v² - u²

Put the above given values in this, we get,

➨ 2 × (-0.5) × s = (0)² - (25)²

➨ -1s = - 625

➨ s = $\bold\blue{625m }$

Hence,

• ➲ Distance Travelled (s) = 625 m

ᴇǫᴜᴀᴛɪᴏɴs ᴏғ ᴍᴏᴛɪᴏɴ :-

• ➊ v = u + at

• ➋ s = ut + 1/2 at²

• ➌ 2as = v² - u²

Here,

a = acceleration

u = initial velocity

v = final velocity

s = distance travelled

t = time taken