Idea of Speed, Distance & Time — Multiple Choice Questions

36 km/hr in m/s is:

1. 72 m/s

2. 10 m/s

3. 15 m/s

4. 18 m/s

Answer

Converting 36 km/hr into m/s (multiply by $\dfrac{5}{18}$) :

36 × $\dfrac{5}{18} = \dfrac{180}{18} = 10$ m/s.

Hence, option 2 is the correct option.

20 m/s in km/h is:

1. 40 km/h

2. 36 km/h

3. 72 km/h

4. 48 km/h

Answer

Converting 20 m/s into km/h (multiply by $\dfrac{18}{5}$) :

20 × $\dfrac{18}{5} = \dfrac{360}{5} = 72$ km/h.

Hence, option 3 is the correct option.

A car covers 120 km in 3 hrs. Distance covered by it, with the same speed, in 5 hrs is:

1. 200 km

2. 180 km

3. 220 km

4. 150 km

Answer

Speed of the car = $\dfrac{\text{Distance}}{\text{Time}} = \dfrac{120}{3} = 40$ km/h.

Distance covered in 5 hours = Speed × Time

= 40 × 5 = 200 km.

Hence, option 1 is the correct option.

You are travelling at a speed of 30 km/h. The time you will take to cover 750 km is:

1. 50 hrs

2. 25 hrs

3. $\dfrac{1}{25}$ hrs

4. none of these

Answer

Time taken = $\dfrac{\text{Distance}}{\text{Speed}} = \dfrac{750}{30} = 25$ hours.

Hence, option 2 is the correct option.

A bus covers 80 km in 2 hrs, next 20 km in 1 hr and last 50 km in 2 hrs. Its average speed is:

1. 100 km/h

2. 60 km/h

3. 30 km/h

4. 50 km/h

Answer

Total distance covered = 80 km + 20 km + 50 km = 150 km.

Total time taken = 2 h + 1 h + 2 h = 5 h.

Average speed = $\dfrac{\text{Total distance covered}}{\text{Total time taken}} = \dfrac{150}{5} = 30$ km/h.

Hence, option 3 is the correct option.

A girl covers 6 km in 30 minutes. Her average speed is:

1. 6 km/min

2. 12 km/h

3. 180 km/min

4. none of these

Answer

Time = 30 minutes = $\dfrac{30}{60}$ h = $\dfrac{1}{2}$ h.

$\text{Average speed} = \dfrac{\text{Distance}}{\text{Time}} \\[1em] = \dfrac{6}{\dfrac{1}{2}} \\[1em] = 6 \times 2 \\[1em] = 12 \text{ km/h}.$

Hence, option 2 is the correct option.

Rohan covers a distance of 24 km and returns back in 3 hrs. His average speed is:

1. 1 km/h

2. 16 km/h

3. 18 km/h

4. none of these

Answer

Since Rohan returns back, total distance = 24 km + 24 km = 48 km.

Total time taken = 3 hours.

Average speed = $\dfrac{\text{Total distance}}{\text{Total time}} = \dfrac{48}{3} = 16$ km/h.

Hence, option 2 is the correct option.

Sangeeta covers first 60 km of her journey at 20 km/h and next 60 km in 2 hrs. Her average speed is:

1. 60 km/h

2. 24 km/h

3. 30 km/h

4. 120 km/h

Answer

Time taken for the first 60 km = $\dfrac{\text{Distance}}{\text{Speed}} = \dfrac{60}{20} = 3$ hours.

Time taken for the next 60 km = 2 hours.

Total distance covered = 60 km + 60 km = 120 km.

Total time taken = 3 h + 2 h = 5 h.

Average speed = $\dfrac{\text{Total distance covered}}{\text{Total time taken}} = \dfrac{120}{5} = 24$ km/h.

Hence, option 2 is the correct option.

A train of length 80 m, moving with uniform speed and passes a pole in 10 s. The speed of the train is:

1. 8 km/h

2. 8 m/s

3. 16 m/s

4. 4 m/s

Answer

To pass a pole (a stationary object), the distance covered = length of the train = 80 m.

Speed = $\dfrac{\text{Distance}}{\text{Time}} = \dfrac{80}{10} = 8$ m/s.

Hence, option 2 is the correct option.

A train of length 80 m passes a platform in 20 s with uniform speed of 10 m/s. The length of the platform is:

1. 120 m

2. 100 m

3. 80 m

4. 800 m

Answer

Distance covered in passing the platform = Speed of train × Time = 10 × 20 = 200 m.

Distance covered in passing the platform = length of the train + length of the platform.

⇒ 200 = 80 + length of the platform

⇒ length of the platform = 200 − 80 = 120 m.

Hence, option 1 is the correct option.