Question

نص السؤال A car, starting from rest and moving with a constant acceleration, travels 200 m in 20 s. What is the magnitude of this acceleration

Answer 1

Given:

Car starts from rest and moves with constant acceleration. It travels 200 in 20 seconds.

To find:

Acceleration of the car

Concept:

Since the acceleration is assumed to be constant ,we can easily apply the the equation of kinematics to find out its value.

Calculation:

$s = ut + \frac{1}{2} a {t}^{2}$

$= > 200 = (0 \times t) + \{ \frac{1}{2} \times a \times {(20)}^{2} \}$

$= > \cancel{ 200} = \cancel{200 }\times a$

$= > a = 1 \: m {s}^{ - 2}$

So acceleration is 1 m/s²

Answer 2

Given

Car starting from rest moving with constant acceleration.

Distance travelled = 200 m

Time taken = 20 s

To find

Magnitude of acceleration of car

Solution

Here, as the car starts from rest so it's initial velocity i.e. u = 0

It has travelled 200 m (s) in 20 s (t)

Using 2nd equation of motion :

⇒ s = ut + ½at²

Putting all values :

➻ 200 = 0 × 20 + ½(a × 20²)

➻ 200 = 0 + ½(a × 400)

➻ 200 = 200a

➻ a = 200/200

➻ a = 1 m/s²

∴ Magnitude of acceleration = 1 m/s²