Motions And Forces

Question 1

Scalar quantity

Answer 1

Only has magnitude
Isn’t direction dependent

Question 2

Vector quantity

Answer 2

Both magnitude and an associated direction

Question 3

How can a vector quantity be represented

Answer 3

Using vector arrows

Question 4

How do vector arrows represent vectors

Answer 4

The length of arrow represents magnitude

Arrow points in associated direction

Question 5

Three examples of vector quantities

Answer 5

1. Velocity
2. Displacement
3. Force

Question 6

Examples of scalar quantities

Answer 6

Temperature
Speed
Mass
Time
Distance
Energy

Question 7

What is velocity

Answer 7

Speed of an object in a specific direction

Question 8

Equation relating average speed, distance and time

Answer 8

Average speed = distance / time

Question 9

On a distance time graph what value does the gradient of the line represent

Answer 9

Speed

Question 10

On a displacement time graph what value does the gradient of the line represent

Answer 10

Velocity

Question 11

What must be done to calculate the speed at a given time from a distance time graph from an accelerating object

Answer 11

Draw a tangent to the curve at the required time
Calculate the gradient of the tangent

Question 12

State equation for the average acceleration of an object

Answer 12

Acceleration (m/s^2) = change in velocity (m/s) / time taken (s)

Question 13

How can the distance travelled by an object be calculated from a velocity time graph

Answer 13

It is equal to the area under the graph

Question 14

On a velocity time graph what does the gradient of the graph represent

Answer 14

Acceleration

Question 15

Typical value for speed of sound

Answer 15

330 m/s

Question 16

Typical value for human walking speed

Answer 16

1.5 m/s

Question 17

Typical value for human running speed

Answer 17

3 m/s

Question 18

Typical value for human cycling speed

Answer 18

6 m/s

Question 19

Approximate value for the acceleration of an object in free fall under gravity near the earths surface

Answer 19

10 m/s^2

Question 20

Name given to the single force that is equivalent to all the other forces acting on a given object

Answer 20

Resultant force

Question 21

Newton’s first law for a stationary object

Answer 21

If the resultant force on a stationary object is zero, the object will remain at rest

Question 22

Newton’s first law for a moving object

Answer 22

If the resultant force on a moving object is zero, the object will remain at constant velocity (same speed in same direction)

Question 23

Defining equation for Newton’s second law

Answer 23

Resultant force = mass x acceleration

F = ma

Question 24

Newton’s second law in words

Answer 24

An objects acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass

Question 25

What is weight

Answer 25

The force that acts on an object due to gravity and the objects mass

Question 26

What quantities does weight depend on

Answer 26

Weight = mass x gravitation field strength Objects mass Gravitations field strength at the given position in the field

Question 27

Unit for weight

Answer 27

Newton

Question 28

Unit for gravitational field strength

Answer 28

N/kg

Question 29

What price of equipment can be used to measure an objects weight

Answer 29

A calibrated spring balance or newton meter

Question 30

When can an object travelling at a constant speed not have a constant velocity

Answer 30

When the object is changing direction E.g moving in a circle

Question 31

Why does an object travelling at a constant speed in a circle not have a constant velocity

Answer 31

Speed is a scalar quantity Velocity is a vector quantity which means it can only be constant if the direction is constant In a circular motion the direction is continuously changing Velocity is constantly changing

Question 32

What is the resultant force that acts on an object moving in a circle called and in which directions does it act

Answer 32

Called the centripetal force and acts towards the centre of the circle

Question 33

What is inertial mass

Answer 33

A measure of how difficult it is to change a give objects velocity The ration of force over acceleration

Question 34

State Newton’s third law

Answer 34

Whenever two objects interact, the forces that they exert on each other are always equal and opposite

Question 35

State the equation used to calculate an objects momentum

Answer 35

Momentum = mass x velocity

Question 36

What is the unit for momentum

Answer 36

kgm/s Kilogram metres per second

Question 37

In a closed system, what can be said about the momentum before and after collision

Answer 37

The total momentum before and after are equal

Question 38

State an equation linking change in momentum, force and time

Answer 38

Force x time = change in momentum

Question 39

How can you measure human reaction times

Answer 39

Using ruler drop test Person A and B hold each end of ruler with 0cm mark at the bottom Pardon A drops ruler without telling B Person B catches is Distance travelled corresponds to their reaction time

Question 40

Why is it important the 0cm mark is at the bottom when doing the ruler test

Answer 40

So you can obtain the distance without having to calculate it

Question 41

What is the stopping distance if a vehicle equal to

Answer 41

The sum of thinking distance and braking distance

Question 42

For a given braking distance, if the vehicles speed is increased, what can be said about its stopping distance

Answer 42

The stopping distance is increased with an increase in speed

Question 43

Give a typical range of values for human reaction time

Answer 43

0.2 - 0.9 seconds

Question 44

Give three factors which can affect a drivers reaction time

Answer 44

Tiredness Drugs Alcohol

Question 45

Give two factors which may affect braking distance

Answer 45

Adverse (wet/icy) road conditions Poor tyre or brake conditions

Question 46

Describe the energy transfers that take place when a car applies its brakes

Answer 46

Work is done by the friction force between the brakes and wheel Kinetic energy of the wheel is converted to heat and is dissipated to the surroundings through brake discs

Question 47

To stop a car in a given distance, if it’s velocity is increased, what must happen to the braking force applied

Answer 47

Braking force must also be increased

Question 48

State two consequences of a vehicle undergoing very large decelerations

Answer 48

Kinetic energy converted to heat is very high causing brakes to overheat Loss of control of the vehicle