Forces

Question 1

What is a scalar quantity?

Answer 1

A quantity that only has a magnitude

Examples include distance and speed.

Question 2

What is a vector quantity?

Answer 2

A quantity that has both a magnitude and a direction

Examples include velocity and force.

Question 3

What is the force of gravity close to the Earth due to?

Answer 3

The planet’s gravitational field strength.

Question 4

What is weight?

Answer 4

The force acting on an object due to gravity.

Question 5

Where can weight be considered to act on an object?

Answer 5

At the object’s centre of mass.

Question 6

How can weight be measured?

Answer 6

Using a calibrated spring-balance (newtonmeter).

Question 7

What is the formula for calculating weight?

Answer 7

Weight (N) = mass (kg) x gravitational field strength (N/kg)

This is denoted as W = mg.

Question 8

How are weight and mass proportional to eachother?

Answer 8

They are directly proportional to each other (W ∝ m).

Question 9

What happens to the weight of an object if its mass doubles?

Answer 9

Its weight also doubles.

Question 10

What defines a force?

Answer 10

A push or pull on an object caused by an interaction with another object.

Question 11

Are forces scalar or vector quantities?

Answer 11

Vector quantities.

Question 12

What are contact forces?

Answer 12

Forces that occur when two objects are touching each other.

Examples include friction, air-resistance, tension, and normal contact force.

Question 13

What are non-contact forces?

Answer 13

Forces that act at a distance without the two objects touching.

Examples include gravitational force, electrostatic force, and magnetic force.

Question 14

What does Newton’s third law state about forces?

Answer 14

When an object exerts a force on another object, it will experience an equal and opposite force.

Question 15

What is a resultant force?

Answer 15

The single force that represents the combined effect of two or more forces acting on an object.

Question 16

How is the resultant force calculated if two forces act in the same direction?

Answer 16

By summing the magnitudes of the forces.

Question 17

How is the resultant force calculated if two forces act in opposite directions?

Answer 17

By finding the difference between the magnitudes of the forces.

Question 18

What does it mean if the resultant force on an object is zero?

Answer 18

The forces are said to be balanced.

Question 19

How can the resultant of two forces that do not act along the same line be found?

Answer 19

By making a scale drawing using a ruler and a protractor.

Question 20

What do free body diagrams represent?

Answer 20

They use arrows to show all of the forces acting on a single object.

Question 21

What does the length of an arrow in a force diagram represent?

Answer 21

The magnitude of the force.

Question 22

What does the direction of an arrow in a force diagram indicate?

Answer 22

The direction of the force.

Question 23

What is the limit of proportionality?

Answer 23

The point beyond which the relationship between force and extension is no longer linear.

Question 24

Fill in the blank: A _______ force is one that acts when two objects are in contact.

Answer 24

contact

Question 25

Fill in the blank: A _______ force acts at a distance without contact.

Answer 25

non-contact

Question 26

Fill in the blank: The _______ of a force shows its magnitude and direction.

Answer 26

arrow

Question 27

What is the definition of gravitational field strength?

Answer 27

The force per unit mass experienced by a small test mass placed in a gravitational field.

Question 28

What is the difference between elastic and inelastic deformation?

Answer 28

Elastic deformation is reversible, while inelastic deformation is permanent.

Question 29

What is a lever?

Answer 29

A simple machine that amplifies an input force to lift or move a load.

Question 30

What is the relationship between extension and force for elastic objects?

Answer 30

The extension of an elastic object is directly proportional to the force, as long as the limit of proportionality is not exceeded. ## Footnote This is described by Hooke's Law.

Question 31

What is the equation used to calculate the spring constant?

Answer 31

force applied (N) = spring constant (N/m) x extension (m) ## Footnote This can be expressed as F = ke.

Question 32

What happens to the extension when compressing an object?

Answer 32

The relationship also applies to compressing an object, where e would be compression instead of extension. ## Footnote This is analogous to the behavior of springs.

Question 33

How can a single force be resolved?

Answer 33

A single force can always be resolved into two component forces at right angles to each other. ## Footnote These are typically referred to as the vertical and horizontal components.

Question 34

What is the moment of a force?

Answer 34

The turning effect of a force. ## Footnote It can be calculated using the equation: moment of a force (Nm) = force (N) x distance (m), or M = Fd.

Question 35

What condition must be met for an object to be balanced?

Answer 35

The sum of the clockwise moments equals the sum of the anticlockwise moments. ## Footnote This is crucial for equilibrium in static systems.

Question 36

Define elastic deformation.

Answer 36

The object can go back to its original shape and size when the forces are removed. ## Footnote This is a key characteristic of materials like rubber and springs.

Question 37

Define inelastic deformation.

Answer 37

The object does not go back to its original shape or size when the forces are removed. ## Footnote Materials like clay exhibit this behavior.

Question 38

How is elastic potential energy calculated?

Answer 38

elastic potential energy (J) = 1/2 x spring constant (N/m) x (extension)² (m²) ## Footnote The equation is often written as Ee = 1/2 ke².

Question 39

What is the function of levers and gears?

Answer 39

They can be used to increase the moment of a force, making it easier to lift or rotate an object. ## Footnote They work by changing the distance from the pivot or altering the gear ratio.

Question 40

What happens when a small gear drives a large gear?

Answer 40

The moment of the applied force is increased but the large gear moves slower. ## Footnote This is a trade-off in mechanical advantage.

Question 41

How does a lever produce a large moment of force?

Answer 41

By allowing force to be applied further from the pivot. ## Footnote This principle is used in tools like crowbars and seesaws.