Question

A car starts from rest and reaches a velocity of 20m/s in 4s.

(a) Find its acceleration

(b) Calculate the distance covered
show your working

Answer 1

Explanation:

acceleration= 20-0/4= 5m/s²

Answer 2

Answer- The above question is from the chapter 'Kinematics'.

Some important terms and formulae:-

1. Velocity- It is the displacement per unit time.

S.I. Unit of Velocity- m/s

It is a vector quantity as it possesses magnitude and direction.

2. Acceleration- It is the rate of change of velocity.

S.I. Unit of Acceleration- m/s²

It is also a vector quantity.

Negative acceleration is called retardation.

3. Distance- It is the path length transversed by an object.

S.I. Unit of Distance- m

It is a scalar quantity.

4. Displacement- It is the shortest distance between the initial and final point.

S.I. Unit of Displacement- m

It is a vector quantity.

5. Equations for uniformly accelerated motion-

Let u = Initial velocity of a particle

v = Final velocity of a particle

t = Time taken

s = Distance travelled in the given time

a = Acceleration

1) v = u + at

2) s = $\frac{1}{2}$ at² + ut

3) v² - u² = 2as

6. Average Speed = Total distance ÷ Total time

7. Average Velocity = Total displacement ÷ Total time

Given question: A car starts from rest and reaches a velocity of 20 m/s in 4s.

(a) Find its acceleration

(b) Calculate the distance covered

Show your working.

Answer: Initial Velocity (u) = 0 m/s

Final Velocity (v) = 20 m/s

Time (t) = 4 s

(a) Acceleration (a) = ?

Using 1st equation of motion, v = u + at

20 = 0 + 4a

4a = 20

∴ a = 5 m/s²

(b) Distance (s) = ?

Using 3rd equation of motion, v² - u² = 2as,

20² - 0² = 2 × 5 × s

s = 400 ÷ 10

∴ s = 40 m