Question

Velocity of car is 30m/s and suddenly a dog comes on the way of car and driver applies brakes and car stops 4 seconds after applying brakes. If total mass of cae is 1000kg then calculate force excerted on car by brakes.​

Answer 1

$\dag\:\underline{\sf AnsWer :}$

In the question we are given the initial velocity (u) as 30 m/s and it is said in question that, suddenly a dog comes on the way of car and driver applies the brakes and car stops so, final velocity (v) will be 0 m/s and time interval (t) is 4 second and it is also given that,the total mass (m) of the car is 1000 kg. We are asked to find the force exerted on car by brakes.

• To solve this numerical first we need to find the acceleration (a) of the car and after finding the acceleration we can find the force exerted on car by brakes by using Newton's second law. So,let's do it :

$:\implies\sf Acceleration = \dfrac{Final \: Velocity - Initial \: Velocity}{Time}$

$:\implies\sf Acceleration = \dfrac{0 - 30}{4}$

$:\implies\sf Acceleration = \dfrac{ - 30}{4}$

$:\implies \underline{ \boxed{\sf Acceleration = - 7.5 \:m/s^2 }}$

$\bigstar \: \underline{\textbf{Force exerted on car by brakes : }}$

$\dashrightarrow\:\:\sf Force = mass \times acceleration$

$\dashrightarrow\:\:\sf Force = 1000 \times - 7.5$

$\dashrightarrow\:\: \underline{ \boxed{\sf Force = - 7500 \:N }}$

Answer 2

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♧Question♧

• Velocity of car is 30m/s and suddenly a dog comes on the way of car and driver applies brakes and car stops 4 seconds after applying brakes. If total mass of car is 1000kg then calculate force excerted on car by brakes.

♧Answer♧

☆initial velocity of the car is 30m/s and and the final velocity will be 0m/s because the driver apply the sudden brakes and it will stop in 4 seconds after applying the brakes and 1000kg is the mass of the car.

Given data:-

• ➠Initial velocity = V1 = 30m/s
• ➠Final velocity = V2 = 0m/s
• ➠Time = t = 4 second
• ➠Mass = m = 1000kg

To find:-

• force exerted on car by applying brakes = ?

Solution:-

☆First we have to find the acceleration because it is need for finding the force.So,

$\large\dashrightarrow{ \sf{Acceleration = \dfrac{Final \: velocity - Initial \: velocity}{time} }} \\ \large\dashrightarrow{ \sf{Acceleration = \dfrac{0 - 30}{4} }} \\\large\dashrightarrow{ \sf{Acceleration = \dfrac{ - 30 }{4} }} \\\large\dashrightarrow{ \sf{Acceleration = -7.5ms^{2} }}$

Now By using force formula,

$\large\dashrightarrow{ \sf{Force = mass \times Acceleration }} \\\large\dashrightarrow{ \sf{Force= 1000 \times - 7.5}} \\ \large\dashrightarrow{ \boxed {\red{\sf{Force= -7,500N}}}}$

☆So -7500N force excerted on car by brakes.

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