Topic 5 - Forces part 2

Question 1

What are the typical values for the speed of walking, running and cycling and sound of air?

Answer 1

Walking - 1.5m/s
Running - 3m/s
Cycling - 6m/s
Sound of air - 330m/s

Question 2

What is a non- uniform motion?

Answer 2

The motion in which the speed is not constant

Question 3

How do you calculate average speed for non- uniform motion?

Answer 3

Average speed = total distance / total time

Question 4

What is the difference between speed and velocity?

Answer 4

Speed is a scalar quantity (magnitude), velocity is a vector quantity (magnitude and direction)

Question 5

What is the difference between distance and displacement?

Answer 5

Distance is the length of the total journey (scalar)

Displacment is the straight line distance between the start and ed points of the journey (vector)

Question 6

How do you calculate average velocity?

Answer 6

Average velocity = displacment / time
v = s/t

Question 7

What is acceleration?

Answer 7

The rate at which an objects velocity changes (m/s)

Question 8

How do you calculate acceleration?

Answer 8

Acceleration = change in velocity / time

Question 9

How can something be moving at a constant speed but changing velocity at the same time?

Answer 9

An object moving in a circular motion (e.g sun) at a steady speed. It dosent have the same constant velocity becuase velocity is a vector quantity and the direction of the journey is constantly changing, if the velocity change son the object it is accelerating.

Question 10

What does a distance time graph tell us?

Answer 10

Straight line - object is at a constant speed the gradient tells us the speed, the steeper the line the faster the object is moving

Horizontal line - object is stationary, a line with a increasing gradinet means the object is accelerating and when decreasing its decelerating

Question 11

How do you determine the speed of an object undergoing uniform motion over a period of time?

Answer 11

The gradient

Question 12

How do you determine the speed of an object undergoing non-uniform motion at a particular point in time?

Answer 12

Draw a tangent to the curve at the time you are interested in then determine the gradient of the tangent

Question 13

What is the equation for gradient?

Answer 13

Gradient = rise / run

Question 14

What does a velocity time graph tell us?

Answer 14

Straight sloping line - object is moving at a constant acceleration, the steeper the line the larger objects acceleration

Horizontal line - objects is moving at a constant speed.

Question 15

What if the acceleration is constant?

Answer 15

If the acceleration is constant then v(squared) - u(squared) = 2as (s=displacement)

Question 16

How do you determine distance travelled from a speed time graph?

Answer 16

Can be obtained by determining the area under a speed-time graph, if the line is not straight then it can be determined by counting squares

Question 17

What is Newton’s first law?

Answer 17

Newtons first law tells us A
an object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force

Question 18

What is Newton’s seccond law?

Answer 18

The acceleration of an object is directly proportinal to the resultant force acting on it and inversely proportional to the mass

Question 19

What is intertial mass?

Answer 19

A measure of how difficult it is to change an objects velocity

resultant force / acceleration that force generates

Question 20

How can Newtons second law be vertified experimentally?

Answer 20

The car:
- The ramp needs to be compensating for friction by tilting so the car travels at a steady speed
- Measure the acceleration: light gate, pulley wheel, weights, string
1. let the car go and as soon as it goes past the light gate stop it and catch the weights, once throught the gate it will record the times and repeat.

Question 21

What happens to the forces and acceleration of a falling object?

Answer 21

It will freefall due to gravity, and will accelerate at 9.8m/s
If the speed continues to increase, it will eventually the reulatnt force on the object is ZERO as it stops accelerating, then it is traveling at terminal velocity

Question 22

What is stopping distance?

Answer 22

The total distance required to stop a moving vehicle

Stopping distance = thinking distance + braking distance

Question 23

What factors affect thinking distance?

Answer 23

• Speed (faster you go the further you travel)
• Drugs/Alcohol ( reaction time)
• Tiredness/illness ( reaction time)
• Distractions (mobile phones)

Question 24

What factors affect braking distance?

Answer 24

• Speed (faster you go the further you travel)
• Condition (breaks, tyres)

Question 25

What energy transfers take place during braking?

Answer 25

kinetic energy of the vehicle to the thermal store of the brakes

Question 26

Why do we stop moving vehicles over a long period of time?

Answer 26

Means that it results in smaller deceleration, and this requires smaller resyltant forces

Question 27

What is momentum?

Answer 27

The tendency of a moving object to remian in motion

momentum = mass x velocity
p = mv

Question 28

What is the conservation of momentum?

Answer 28

In a closed system, the total momentum before an event is equal to the total momentum after an event

Question 29

What is a vector?

Answer 29

has a direction and magnitude

Question 30

What is a scalar?

Answer 30

only has magnitute

Question 31

What are examples of vectors?

Answer 31

weight
displacement
velocity
acclelration
momentum
forces

Question 32

what are example of scalars?

Answer 32

distance
time
mass
energy
temperature
speed

Question 33

What is the centre of mass?

Answer 33

The point where we consider the weight to acct from

Question 34

What is the equation of spring constant?

Answer 34

k=f/e

spring constant = force / extension