Dynamics

Question 1

Which quantity can be completely described by its magnitude and direction?

Answer 1

A vector quantity can be completely described by its magnitude and direction.

Question 2

What are three ways to reduce friction?

Answer 2

Three ways to reduce friction are lubrication, smooth surfaces, streamlining…

Question 3

What is the energy change when a ball is thrown up in the air?

Answer 3

When a ball is thrown up in the air, the energy change is

kinetic energy to potential energy.

Question 4

What is Newton’s 1st Law?

Answer 4

If the forces on an object are balanced, then the object will either

• stay at rest
• move with a constant velocity in a straight line

Question 5

For projectile motion, what is the only equation you should use for the vertical part of the motion?

Answer 5

For the vertical part of the motion, the only equation which should be used is

Question 6

For projectile motion, what is the only equation you should use for the horizontal part of the motion?

Answer 6

For the horizontal part of the motion, the only equation which should be used is

Question 7

Name the three quantities shown in this formula.

Answer 7

W = work done

F = unbalanced force

d = distance

Question 8

What is a projectile?

Answer 8

A projectile is an object which is moving only under the influence of gravity.

(assume that air resistance is negligible)

Question 9

What is the definition of a vector quantity?

Answer 9

A vector quantity has both

magnitude and direction.

Question 10

Give 5 examples of scalar quantities.

Answer 10

Speed, distance, mass, time, energy.

Question 11

Name the three quantities shown in this formula.

Answer 11

s = displacement

v = velocity

t = time

Question 12

What three things can a force change?

Answer 12

A force can change an object’s shape, speed or direction.

Question 13

What does the prefix G stand for?

Answer 13

G stands for giga

giga = x 10⁹

Question 14

Which quantity is represented by the symbol v , in the equation shown?

Answer 14

v = velocity

Question 15

Use Newton’s 3rd Law to explain how a rocket accelerates.

Answer 15

Newton’s 3rd Law is about action and reaction forces.

In a rocket, the rocket pushes the combustion gases downwards, and the gases push back up against the rocket (causing it to accelerate).

Question 16

What is meant by the statement,

“An object has an acceleration of 5 ms^-2” ?

Answer 16

This means the object’s velocity is increasing by 5 ms^-1 every second.

Question 17

What is the energy change when a ball is dropped?

Answer 17

When a ball is dropped, the energy change is

potential energy to kinetic energy.

Question 18

What is the unit for work done?

Answer 18

The unit for work done is joules (J).

(work done is an amount of energy transferred)

Question 19

For projectile motion, why is this the only equation you should use for the horizontal part of the motion?

Answer 19

For the horizontal part of the motion, the velocity is constant.

Question 20

What is the unit for speed?

Answer 20

The unit for speed is

metres per second

(ms^-1)

Question 21

What is meant by terminal velocity?

Answer 21

When a falling object (e.g. a skydiver) accelerates, the air resistance acting against the object increases, until it is balanced with the object’s weight. When the forces are balanced, it will travel at a constant speed (called ‘terminal velocity’).

Question 22

What does the prefix M stand for?

Answer 22

M stands for mega

mega = x 10⁶

Question 23

Name the three quantities shown in this formula.

Answer 23

F = unbalanced force

m = mass

a = acceleration

Question 24

What is the energy change when a car applies its brakes?

Answer 24

When a car applies its brakes, the energy change is

kinetic energy to heat energy.

Question 25

What is the definition of a **scalar** quantity?

Answer 25

A **scalar** quantity has **magnitude** only.

Question 26

What does the prefix **µ** stand for?

Answer 26

**µ** stands for **micro** **micro** = **x 10^-6**

Question 27

What is **Newton's 3rd Law**?

Answer 27

**Newton's 3rd Law** states that **for every 'action' force** there is an **equal but opposite 'reaction' force**.

Question 28

What is the **unit** for **time**?

Answer 28

The **unit** for **time** is ## Footnote **seconds** (**s**)

Question 29

What is the **unit** for **velocity**?

Answer 29

The **unit** for **velocity** is ## Footnote **metres per second** (**ms^-1**)

Question 30

What does the prefix **n** stand for?

Answer 30

**n** stands for **nano** **nano** = **x 10^-9**

Question 31

What is meant by **balanced forces**?

Answer 31

Balanced forces means forces which are the **same size** but in **opposite directions**.

Question 32

What is the difference between **mass** and **weight**?

Answer 32

**Mass** is a measure of the amount of 'stuff' that makes up an object. **Weight** is the force due to gravity acting on an object.

Question 33

What is the **unit** for **displacement**?

Answer 33

The **unit** for **displacement** is ## Footnote **metres** (**m**)

Question 34

What does the prefix **k** stand for?

Answer 34

**k** stands for **kilo** **kilo** = **x 10³**

Question 35

Which quantity is represented by the symbol **E_p**?

Answer 35

**E_p** = **potential energy**

Question 36

Is the **mass** of an object **constant** at all points in the universe?

Answer 36

**Yes**. The **mass** of an object does not change, regardless of the force of gravity. 1kg on Earth would be 1kg on the Moon, 1kg in outer space, and so on.

Question 37

What is the **unit** for **mass**?

Answer 37

The **unit** for **mass** is **kilograms** (**kg**)

Question 38

What is **Newton's 2nd Law**?

Answer 38

If the **forces** on an object are **unbalanced**, the object will **accelerate** in the direction of the unbalanced force. ## Footnote **F = m x a**

Question 39

What does the prefix **m** stand for?

Answer 39

**m** stands for **milli** **milli** = **x 10^-3**

Question 40

Give 5 examples of vector quantities.

Answer 40

Velocity, displacement, weight, force, acceleration.

Question 41

If the **forces** acting on the balloon are **balanced**, describe the motion of the balloon. *(there are two possible answers!)*

Answer 41

If the **forces** acting on the balloon are **balanced**, the balloon will ## Footnote * stay at rest OR * move at a constant speed in a straight line

Question 42

By referring to the **horizontal** and **vertical** parts of its motion, explain the **curved path** of a **projectile**.

Answer 42

A projectile has **constant horizontal velocity** and **constant vertical acceleration**.

Question 43

Name as many different types of **energy** as possible.

Answer 43

**Kinetic, potential, electrical, chemical, light, heat, sound, nuclear**

Question 44

What is meant by **acceleration**?

Answer 44

**Acceleration** is the **change in velocity** **per second.**

Question 45

For projectile motion, why is this the **only** equation you should use for the **vertical** part of the motion?

Answer 45

For the **vertical** part of the motion, the **acceleration is constant** (it's **not** a constant velocity).

Question 46

What is the **unit** for **weight**?

Answer 46

The **unit** for **weight** is ## Footnote **newtons** (**N**)

Question 47

Name the **forces** acting on a hot-air balloon, accelerating upwards.

Answer 47

The balloon would have **weight** acting downwards and **upthrust** (or buoyancy) acting upwards.

Question 48

Which quantity is represented by the symbol **g**?

Answer 48

**g** = **gravitational field strength**

Question 49

Which quantity is represented by the symbol **E_k**?

Answer 49

**E_k** = **kinetic energy**

Question 50

What is **friction**?

Answer 50

**Friction** is a **force** which opposes an object's motion. Friction occurs when two surfaces come in contact with each other.

Question 51

What is the energy change in a **washing machine**?

Answer 51

In a washing machine, the energy change is **electrical energy** to **heat** and **kinetic energy**.

Question 52

Name the three quantities shown in this formula.

Answer 52

d = distance v = speed t = time

Question 53

Is the **weight** of an object constant at all points in the universe?

Answer 53

**No** - the **weight** of an object depends on its mass *and* the **gravitational field strength**. Therefore, the weight of an object can vary at different points in the universe.

Question 54

What is the **unit** for **distance**?

Answer 54

The **unit** for **distance** is ## Footnote **metres** (**m**)

Question 55

How would you calculate **distance** from a velocity-time graph?

Answer 55

Distance = **area under a velocity-time graph**

Question 56

What is the **unit** for **acceleration**?

Answer 56

The **unit** for **acceleration** is ## Footnote **metres per second *squared*** (**ms^-2**)

Question 57

Name the four quantities shown in this formula.

Answer 57

a = acceleration v = final velocity u = initial velocity t = time

Question 58

What is the **unit** for **force**?

Answer 58

The **unit** for **force** is ## Footnote **newtons** (**N**)

Question 59

What is the **unit** for **energy**?

Answer 59

The **unit** for **energy** is ## Footnote **joules** (**J**)

Question 60

Which quantity can be completely described by its **magnitude** *only* ?

Answer 60

A **scalar** quantity can be completely described by its **magnitude** only.