Forces

Question 1

what is a scalar quantity?

Answer 1

something that only has magnitude (size)

Question 2

three examples of scalar quantities

Answer 2

• mass
• temperature
• speed

Question 3

what is a vector quantity?

Answer 3

something that has both direction and magnitude

Question 4

three examples of vector quantities

Answer 4

• velocity
• weight
• force !!

Question 5

define what a force is

Answer 5

a push, pull, or twist that acts on an object due to interaction with other objects

Question 6

what is force measured in?

Answer 6

newtons (N)

Question 7

three examples of a contact force

Answer 7

• friction
• air resistance
• reaction

Question 8

three examples of non-contact forces

Answer 8

• gravity
• magnetism
• electrostatic

Question 9

define what weight is

Answer 9

a force due to gravity

Question 10

what is weight measured in?

Answer 10

newtons (N)

Question 11

what is the equation for weight?

Answer 11

weight = mass x gravitational field strength

Question 12

what is the connection between weight and mass?

Answer 12

they are directly proportional to one another

Question 13

define resultant force

Answer 13

a single force that is used to represent a number of forces acting on an object

Question 14

what is the connection between work done and energy transfer?

Answer 14

whenever work is done, energy is transferred

Question 15

key fact about elastic materials

Answer 15

they will always return to their original shape if we take away the forces acting on them

Question 16

define elastic limit

Answer 16

the point at which a spring does not go back to it’s original shape

Question 17

what’s the connection between work done and elastic potential energy?

Answer 17

the work done is equal to the elastic potential energy

Question 18

describe the differences between distance and displacement (2)

Answer 18

DISTANCE
- only shows how far
- scalar quantity (only has magnitude)

DISPLACEMENT
- shows how far an object travels in a given direction
- vector quantity (has both magnitude and direction)

Question 19

what is the typical walking speed?

Answer 19

1.5 m/s

Question 20

what is the typical running speed?

Answer 20

3 m/s

Question 21

what is the typical cycling speed?

Answer 21

6 m/s

Question 22

what is the speed of sound in air?

Answer 22

330 m/s

Question 23

how can you work out the speed of sound? (5)

Answer 23

• stand near a wall in a place that echoes (hall, sports hall)
• two people: one holds the stopwatch, one claps their hands
• measure your distance from the wall
• time how long from clapping that the echo is heard for
• use the speed equation

Question 24

define velocity

Answer 24

speed in a given direction

Question 25

what is the **one** difference between calculating speed and calculating velocity?

Answer 25

when calculating velocity, the answer must state the direction in which the object is moving in *e.g - 1.25 m/s south*

Question 26

how do you work out the gradient from a distance-time graph?

Answer 26

gradient = distance travelled ------------- time taken

Question 27

define **acceleration**

Answer 27

how fast there is a change in an object's velocity

Question 28

what exactly does the gradient of a **velocity-time** graph tell us?

Answer 28

the acceleration

Question 29

define **deceleration**

Answer 29

negative acceleration

Question 30

how do you work out **displacement** from a **velocity-time graph**?

Answer 30

calculate the total area under the graph

Question 31

define **terminal velocity**

Answer 31

when the forces acting against an object balance and the object therefore stops accelerating and moves at a constant velocity

Question 32

**Newton's First Law** (3)

Answer 32

> if a force acts on a stationary object, it will cause it to move > if a force acts on a moving object, the object will either: 1. slow down 2. speed up 3. change direction > if the overall force is balanced then... - a stationary object will remain stationary - a moving object will continue to move at a constant speed

Question 33

**Newton's Second Law** (3)

Answer 33

> force is directly proportional to mass - the greater the mass, the larger the force it will exert > force is directly proportional to acceleration - the greater the force, the greater the acceleration > acceleration is inversely proportional to mass - the greater the mass, the less acceleration to mass

Question 34

**Newton's Third Law**

Answer 34

> whenever two objects interact, the forces they exert on each other are equal and opposite

Question 35

define **stopping distance**

Answer 35

the overall time taken to stop after seeing an obstruction

Question 36

what makes up stopping distance?

Answer 36

thinking distance + breaking distance

Question 37

define **thinking distance**

Answer 37

time taken to apply the break once seeing an obstruction

Question 38

define **breaking distance**

Answer 38

how long it takes the car to stop after the break has been applied

Question 39

list the factors that affect thinking distance (6)

Answer 39

- speed - age - distractions - tiredness - alcohol - drugs

Question 40

list the factors that affect breaking distance (3)

Answer 40

- speed - brake conditions - weather

Question 41

list the dangers of rapid deceleration (2)

Answer 41

- driver could lose control of the car - brakes overheat

Question 42

**conservation of momentum**

Answer 42

total momentum after the event is equal to the total momentum before the event