Motion

Question 1

is distance a scalar or vector quantity? why?

Answer 1

scalar because it only has a
magnitude or size

Question 2

is displacement a scalar or vector quantity? why?

Answer 2

vector quantity as it has size and direction.

Question 3

what is displacement?

Answer 3

Quantity describing the distance from the start of the journey to the end in a straight line with a described direction, eg 50 km due north of the original position.

Question 4

how can you express a displacement in a diagram?

Answer 4

with an arrow to show the direction and the length of an arrow represents the magnitude of the quantity through using a scale

Question 5

what factors affect the speed at which a person can walk, run or cycle?

Answer 5

• age
• terrain
• fitness
• distance travelled

Question 6

what is the typical speed for walking?

Answer 6

1.5m/s

Question 7

what is the typical speed for running?

Answer 7

3m/s

Question 8

what is the typical speed for cycling?

Answer 8

6

Question 9

why does the speed of wind through air vary?

Answer 9

• when it passes over or around certain objects, such as trees, it can experience some friction *this leads to turbulence in the air, which in turn changes the speed of the wind
• the temperature and the pressure of the air can also affect wind speed.

Question 10

why does the speed of sound through air vary?

Answer 10

• when sound waves pass through objects of different densities
• the more dense the object, the slower the sound will travel.

Question 11

is velocity a scalar or vector quantity?

Answer 11

vector

Question 12

is speed a scalar or vector quantity?

Answer 12

scalar

Question 13

why does motion in a circle involve constant speed but changing velocity? give an example

Answer 13

*When a body moves in a circle, its direction is constantly changing.
*Since velocity is a vector quantity, having both a size and a direction, the velocity of the body must be changing even though its speed is constant.
* a car travelling on a roundabout will move at a constant speed, but with a changing velocity, as its direction is constantly changing

Question 14

what does the area under a velocity-time graph represent?

Answer 14

displacement

Question 15

what is acceleration measured in?

Answer 15

m/s²

Question 16

what does the gradient of the line on a velocity-time graph represent?

Answer 16

acceleration

Question 17

what is terminal velocity?

Answer 17

• the maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces
• at terminal velocity, the object moves at a steady speed in a constant direction because the resultant force

Question 18

what is resultant force?

Answer 18

The single force that could replace all the forces acting on an object, found by adding these together. If all the forces are balanced, the resultant force is zero.

Question 19

what happens after a skydiver leaves the aircraft?

Answer 19

1. the skydiver accelerates downwards due to the force of gravity (weight). there’s no air resistance acting in the upwards direction, and there is a resultant force acting downwards so the skydiver accelerates towards the ground
2. they gain speed. their weight stays the same but the air resistance increases. there is still a resultant force acting downwards, but this gradually decreases.
3. eventually, the skydiver’s weight is balanced by the air resistance. there is no resultant force and the skydiver reaches terminal velocity.
4. when the parachute opens, the air resistance increases and is greater than the weight. the skydiver slows down until a new, lower terminal velocity is reached.
5. when they hit theground, the forces are balanced with a constant speed of zero

Question 20

how does an object falling from rest through a fluid due to gravity reach its terminal velocity?

Answer 20

1. at the start, the object accelerates downwards due to the force of gravity
2. as the object’s speed increases, frictional forces such as air resistance or drag increase
3. at terminal velocity, the weight of the object due to gravity is balanced by the frictional forces, and the resultant force is zero