Forces

1. 1. A force is a _ or a pull.

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

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

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

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

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

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

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

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

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