2a. A force can cause an object at rest to _.

(a)  

2b. A force can_, or change the speed or the _ of a moving object.

(a)  

2c. A force can change the _ of an object.

(a)  

3. 3a. _ force opposes motion when two surfaces are in contact.

3b. Frictional force _ when two surfaces are in contact.

(a)  

4a._ force is exerted by a spring when it is stretched or compressed.

(a)  

4b. Elastic spring force is exerted by a spring when it is _ or _.

(a)  

5a. _ force is a force of attraction between two objects.

(a)  

5b. Gravitational force is a force of _ between two objects.

(a)  

6a. _ is the amount of gravitational force acting on an object.

(a)  

6b. Weight is the amount of (a)   acting on an object.

6c. _ is the amount of substance in an object.

(a)  

7a. _ force is a force exerted by a magnet.

(a)  

7b. Magnetic force is a force _.

(a)