Question

The speed of a car is 72km / hour before finally experiencing acceleration and then stops within 10 seconds. Determine the acceleration of the car and how much distance traveled

Answer 1

Answer:

A car moves with a velocity of 72 km/hr it is brought to rest in 10 seconds. What was the velocity, and the retardation?

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acceleration = (final velocity - initial velocity) / time

Initial velocity(Vi) = 72km/h = 72,000 m/h. (A kilometre is 1000 metres)

There are 3600 seconds in an hour, so

Vi = 72,000/3600= 20m/sec. Final velocity(Vf) = 0

Vf - Vi = 0–20 = -20m/sec.

So deceleration is -20/10 = -2m/sec/sec (metres per second squared)

(The minus indicates deceleration)

What this means is that the car loses speed at a uniform rate of 2m/sec,

so after 1 second, velocity = 18m/sec, after 2 secs, 16m/sec…..etc.

Answer 2

QUESTION

The speed of a car is 72 km/hr before acceleration and then stops within 10 seconds . Determine the acceleration of the car and how much distance it had travelled ?

ANSWER

Given : -

Speed of a car is 72 km/hr before acceleration and then it stops within 10 seconds

Required to find : -

• Acceleration of the car ?

• Distance travelled by the car ?

Equations used : -

v = u + at

v² - u² = 2as

Solution : -

Speed of a car is 72 km/hr before acceleration and then it stops within 10 seconds

we need to find the ;

• Acceleration of the car ?

• Distance travelled by the car ?

So,

From the given data we can conclude that ;

Initial velocity of the car ( u ) = 72 km/hr

Final velocity of the car ( v ) = 0 km/hr

Time ( t ) = 10 seconds

Here,

we need to convert this Initial velocity from km/hr into m/s because the time is given seconds .

As we know that ;

1 km/hr = 5/18 m/s

72 km/hr = ?

=> 72 x 5/18

=> 4 x 5

=> 20 m/s

72 km/hr = 20 m/s

Similarly,

0 km/hr = 0 m/s

Hence,

Initial velocity of the car ( u ) = 20 m/s

Final velocity of the car ( v ) = 0 m/s

Using the equation of the motion ;

i.e. v = u + at

=> 0 = 20 + a x 10

=> 0 - 20 = a x 10

=> - 20 = 10a

=> 10a = - 20

=> a = - 20/10

=> a = - 2 m/s²

Hence,

• Acceleration of the car = - 2 m/s²

Since,

The acceleration is negative . we can say that it is decelerating .

Now,

Let's find the distance travelled during this acceleration .

Using the equation of motion ;

i.e. v² - u² = 2as

=> ( 0 )² - ( 20 )² = 2 x - 2 x s

=> 0 - 400 = 2 x - 2 x s

=> - 400 = - 4 x s

=> - 400 = - 4s

Taking - ( minus ) common

=> - ( 400 ) = - ( 4s )

- ( minus ) get's cancelled

=> 400 = 4s

=> 4s = 400

=> s = 400/4

=> s = 100 meters

Hence,

• Distance travelled ( s ) = 100 meters

Therefore,

Acceleration of the car = - 2 m/s²

Distance travelled = 100 meters