Question

The distance covered by a car in 400 km in 8 hrs. Calculate the speed in m/s

Answer 1

Answer:

Speed = 13.88 m

Explanation:

Distance = 400km

Time = 8hrs

Speed = Distance ÷ Time

Speed = 400 ÷ 8

Speed = 50 km/hr

Speed = 13.88 m/s (divide kmph by 3.6)

ans) Speed of car = 13.88 m/s

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

8. Some basic formulae using calculus method:

1) Velocity = $\frac{dx}{dt}$

2) Acceleration = $\frac{dv}{dt}$

3) Acceleration (when x is given) = $v \frac{dv}{dx}$

9. Unit conversion:

1 km = 1000 m

⇒ 1000 m = 1 km

1 m = $\frac{1}{1000}$ km

1 hour = 60 minutes

1 minute = 60 seconds

⇒ 1 hour = 60 × 60 = 3600 seconds

3600 seconds = 1 hour

1 second = $\frac{1}{3600}$ hour

To convert from m/s to km/h. multiply by $\frac{5}{18}$.

We can obtain this by:-

1 m/s = $\frac{1}{1000} * \frac{3600}{1}$ km/h

1 m/s = $\frac{18}{5}$ km/h (by simplification).

Similarly, to convert from km/h to m/s, multiply by $\frac{5}{18}$ .

Given question: The distance covered by a car in 400 km in 8 hrs. Calculate the speed in m/s.

Answer: Distance = 400 km

Time = 8 hrs

Speed = $\frac{Distance}{Time}$

Speed = $\frac{400}{8}$

Speed = 50 km/hr

We know that, to convert from km/h to m/s, multiply by $\frac{5}{18}$.

So, speed = $50 \times \frac{5}{18}$ = 13.89 m/s

∴ Speed of the car = 13.89 m/s.