2.2 Forces & Motion

Question 1

Gravity

Answer 1

Attracts all masses, but you only notice when the mass is huge, gives everything a weight

Question 2

Mass

Answer 2

Amount of stuff in an object - directly proportional to weight and when increasing mass you increasing weight
Weight = mass x GF

Question 3

Weight

Answer 3

Force acting on an object due to gravity and is caused by gravitational field around it - changes with location - measured as newtrons using a calibrating spring

Question 4

Gravitational Field

Answer 4

Strength of an object varies with location, gets strong the closer to Earth core

Question 5

Resultant Force

Answer 5

Overall force on a point or object

Question 6

Forces

Answer 6

Decides whether the object accelerates, decelerates, etc - number of forces act on a single point you can replace them with RF - things don’t move because another force of the same size is acting in the opposite direction

Question 7

Non-zero Resultant Force

Answer 7

It’s unbalanced, will either accelerate or decelerate, forces are unbalanced

Question 8

On a car when

Answer 8

Thrust is greater than drag it will go forward - normal contact force acting on a car balances it out

Question 9

Newtons First Law

Answer 9

No resultant force means no velocity change - object remains at rest unless acted on by an external force

Question 10

No Resultant Force on a moving object means

Answer 10

It will just carry on moving at the same velocity - accelerate in direction of force - starting, stopping, speeding up and slowing down

Question 11

Newtons Second Law

Answer 11

No zero resultant force causes acceleration - RF = mass x acceleration - acceleration of a body is directly proportional to mass

Question 12

Rocket Force

Answer 12

1) rocket accelerates by burning fuel to create upward thrust which is greater then downwards weight and air resistance
2) when mass decreases acceleration increases, weight decreases due to mass + GF strength
3) atmosphere gets thinner = air resistance decreasing, so resultant upward force + acceleration increases
4) rocket in space has now weight or air resistance but loses mass as it uses fuel to accelerate

Question 13

Terminal Speed

Answer 13

Friction and drag will slow things down - when an object is moving friction acts in the opposite direction and movement

Question 14

Friction

Answer 14

Makes things slow down so you need a driving force to keep it moving

Question 15

Drag

Answer 15

Occurs when an object passes through a fluid, to reduce drag in fluids keep the shape of the object streamline - parachutes work in the opposite way

Question 16

Objects Setting off

Answer 16

They have more driving force than friction force - speed increases = resistance increases - gradually reducing resultant force is equal to driving force - forces are balanced and object meets maximum speed

Question 17

Skydiving

Answer 17

1) skydiver accelerates through air and weight becomes greater than air resistance
2) air resistance increases as speed increases until weight = air resistance
3) parachute opens causing air resistance to increase weight is now less than air resistance
4) speed decreases air resistance also decreasing until weight = air resistance

Question 18

Terminal Speed Practical

Answer 18

1) pointer is set up and prepare to drop cupcake casings at at least 150 cm
2) drop cup cake casings by adding more or dropping from a higher point

Question 19

Inertia

Answer 19

Measures how difficult it is to change objects velocity - determine mass of an object - larger the mass the larger the inertia = harder to change velocity
Mass = force divided by acceleration
Large mass = large resultant force

Question 20

Newtons Third Law

Answer 20

Reaction forces are equal and opposite- if body A exerts force on body B then body B exerts an equal and opposite force to body A - if you push something it will push against you

Question 21

Two forces acting on different objects

Answer 21

When a rocket burns fuel it pushes hot gases out of the bottom of the rocket - rockets exert backward force on gas - hot gases exert an equal/opposite force on rocket

Question 22

Terminal Velocity

Answer 22

defined as the highest velocity attained by an object falling through a fluid. It is observed when the sum of drag force and buoyancy is equal to the downward gravity force acting on the object. The acceleration of the object is zero as the net force acting on the object is zero