5082421
Description
Flashcards by Yeung Kam Fan, updated more than 1 year ago
|
Created by Yeung Kam Fan
over 9 years ago
|
|
| Question | Answer |
| 9 . 1 When we apply a force on an object , what will happens to the object ? | 1 ) Change the speed of the object 2 ) Change the direction in which the object moves 3 ) Change the shape of an object |
| There are two kinds of forces , states them. | 1 ) Contact force : When one object applies a force on another object through direct object . 2 ) Non-contact force : An object apply a force on another object that is not in direct contact |
| Gives some example of the two kinds of force . | 1 ) Contact force : Push / pull the doors 2 ) Non-contact force : Force of gravity / magnetic force |
| In the laboratory , How can we measure the forces ? | We can measure forces by a newton balance or spring balance . The unit of force is the newton ( N ). |
| 9 . 2 What is friction ? | Whatever an object slides over or tends to slide over another object , a force arises to oppose this change . It is friction . It is a contact force .Friction always oppose the motion or the tendency of motion of an object. |
| What is air resistance ? | When an object moves through air or water , there are opposing force acting on an object by air . It is called the air resistance . |
| Briefly explain the heating effect of friction . | When an object moves against friction , kinetic energy changes to heat energy. |
| Why we need to reduce the friction ? | 1 ) Since the friction opposes the motion of an object , it can slow down and even stop the object. 2 ) The object wears out as it moves against friction . 3 ) The kinetic energy of the object is changed to heat energy , which is often unnecessary and leads to a waste of energy . |
| How can we reduce the friction ? | 1 ) Using rolling beads 2 ) Supporting the object on an air cushion 3 ) Adding lubricant between the object and the surface . 4 ) Streamlining an object |
| 9 . 3 What is the force of gravity ? | The Earth pulls an object towards its centre even when it is not direct contact with the object. This is called the force of gravity .it is a non-contact force . |
| What is mass ? | 1 ) Mass shows the amount of matter in the object . 2 ) It can be measured in kilogram ( kg ) or gram ( g ). 3 ) For a certain object , its matter is the same in all places , nits mass is also the same in all place . |
| What is weight ? | 1 ) weight id the Earth's force gravity acting on an object 2 ) It can be measured in newton ( N ) 3 ) For a certain object , weight can different in different locations , where the force of gravity is different . |
Want to create your own Flashcards for free with GoConqr? Learn more.