# 8th Science Refresher course Topic 3 - Answer key

## Lesson 3 - Force and Motion - Refresher course Answer

EVALUATION

#### 1. Choose the correct answer

1. The average speed of a car which travels 60 km in 3 hours

(a ) 10 km / h

(b ) 20 km / h

( c ) 30 km / h

(d ) 60 km / h

2. How the speed differs from velocity

(a) speed is velocity in a given direction

(b) velocity is speed in a given direction

(c) They are the same

3. A car moves 80 km to the south, what is its displacement

(a) 20km south

(b) 50km east

(c) 80km south

(d) 160km north

4. A particle moves in a circular path of radius “r“ ,what is the displacement of the particle

after passing half of the circular path

(a) zero

(b) r

(c) 2r

(d) r/2

5.Acceleration is the measure of the change in ----------

(a) density

(b) motion

(c) velocity

(d) mass

#### II. Fill in the blanks

1. Minimum distance between the two places in straight line path ----------

2. The rate of change of velocity ---------------- .

3. It he velocity of a particle increases with respect to time, it gets ------------- acceleration.

4. In Speed—Time graph, the slope line gives ---------. value.

5. SI unit of velocity is --------------.

6. The negative acceleration is called as ------------------.

7. Speed is a ---------- quantity.

8. Velocity has ----------- value and ---------- value .

9. Distance is ------------ measurement.

10. SI unit of acceleration is --------------- .

### III. Match the following

1. Displacement-a = (v- u ) / t

2. Speed- Uniform velocity

3. Acceleration- Metre (m)

4. Velocity - Distance / Time

5. Speed of light in vaccum -Displacement / Time