1 Forces and shape

Question 1

What are the types of forces?

Answer 1

• Gravitational (weight)
• Electrostatic
• Thrust
• Upthrust
• Air resistance (drag)
• Compression
• Tension
• Reaction force

Question 2

What is gravitational (weight) force?

Answer 2

The force between any two objects with mass.

Question 3

What is electrostatic force?

Answer 3

The force between any two objects with charge (like a proton and an electron).

Question 4

What is thrust?

Answer 4

The force pushing a vehicle (like the push from rocket engines on the shuttle).

Question 5

What is upthrust?

Answer 5

The upward force on any object in a fluid (like a boat on the surface of a river).

Question 6

What is air resistance (drag)?

Answer 6

The force of friction between objects falling through the air (like a skydiver in freefall).

Question 7

What is compression force?

Answer 7

Forces that squeeze an object (like squeezing a spring).

Question 8

What is tension force?

Answer 8

Forces that stretch an object (like two teams in a tug-of-war).

Question 9

What is the reaction force?

Answer 9

The force between any two objects in contact (like the upwards force from a table on a book).

Question 10

What is a normal reaction?

Answer 10

That means its acting at 90* to the road surface.

Question 11

How to calculate resultant forces?

Answer 11

Force acted on one side - force acting on the other side.

Question 12

What is friction?

Answer 12

It is a force that opposes motion.

Question 13

What is a vector quantity?

Answer 13

A quantity with magnitude and direction.

Question 14

What is a scalar quantity?

Answer 14

A quantity that only has magnitude.

Question 15

What is magnitude?

Answer 15

How much of a quantity.

Question 16

What type is quantity is force?

Answer 16

Vector quantity.

Question 17

What is the elastic behaviour of a material?

Answer 17

The ability of a material to recover its original shape after the forces causing deformation have been removed.

Question 18

What does Hooke’s law state?

Answer 18

The extension of an object is directly proportional to the force causing it.

Question 19

What are the steps taken to investigate how the extension of a spring changes with load?

Answer 19

• The length of the unstretched spring is measure with a half-meter ruler.
• The spring is then loaded with different weights.
• The extension is then recorded into a table of results.
• You then plot a graph of force (N) to extension (m).

Question 20

How do you know if a spring obeys Hooke’s law?

Answer 20

Question 21

When does Hooke’s law apply?

Answer 21

When you don’t stretch a spring too far.

Question 22

What happens if a spring is stretched beyond its elastic limit?

Answer 22

It will not return back to its original length even if you take the weights off of the spring.

Question 23

What does a force - extension graph look like if a spring has surpassed its elastic limit?

Answer 23

Question 24

What other things can you use this test on?

Answer 24

• Wires
• Rubber bands.

Question 25

Do wires obey Hookes law?

Answer 25

It depends on the metal used - some will obey the law until the wire breaks; other types will stretch elastically and then plastically before breaking.

Question 26

Do elastic bands obey Hookes law?

Answer 26

The graph that is produced when replicating the experiment is not a straight line - showing that it doesn’t obey Hooke’s law.

Question 27

What does a typical force-extension graph look like for elastic bands?

Answer 27