# 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**

**Answer : **

**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**

**Answer : **

**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**

**Answer : **

**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**

**Answer : **

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

**(a) density**

** (b) motion**

**(c) velocity **

**(d) mass**

**Answer : **

#### II. Fill in the blanks

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

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

**Answer : **

### 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**

**Answer : **