Understanding Normal Force

In science the word normal means:
1. perpendicular
2. parallel
3. non-plural
4. standard
Which of these arrows is the normal to the surface?
1. A
2. B
3. C
4. D
Which of these arrows is the normal to the surface?
1. A
2. B
3. C
4. D
Which of these arrows is the normal to the surface?
1. A
2. B
3. C
4. D
There are two ways to think of the normal force: the supporting force or the pressing force. The idea of the supporting force is helpful to calculate the normal force. The idea of the pressing force helps you realize why an increase in normal force increases the friction.

How much normal force is there between the 3 kg and 6 kg object? (Remember to use forces not masses.)
Don't include units in your answer.
1. 30
2. 60
3. 90
4. 150
5. 180
How much normal force is there between the 6 kg and 9 kg object? (No units.)
1. 30
2. 60
3. 90
4. 150
5. 180
How much normal force is there between the 9 kg object and the table? (No units.)
1. 30
2. 60
3. 90
4. 150
5. 180
Which surface will have the most friction (assuming they have the same coefficient of friction)?
1. A
2. B
3. C
How much normal force does the table have to support? (No units.)
1. 50
2. 12
3. 120
4. 100
5. 140
How much normal force does the table have to support? (No units.)
1. 30
2. 12
3. 90
4. 100
5. 150
If M₁ = 6 kg, how much normal force is there on M₁?
1. 0 N
2. 3 N
3. 6 N
4. 60 N
5. Not enough information