Force And Motion

Question 1

Why do objects recoil in explosions.

Answer 1

Objects needs to have equal momentum in the explosion e.g rowing boat recoils as it needs to have equal momentum to the Person jumping off it

Question 2

What happens if impact time is made longer

Answer 2

Force and momentum decrease

Question 3

What happens to a moving objects momentum if no forces act on it

Answer 3

It stays the same

Question 4

What happens when an object is thrown in the air

Answer 4

Gravity decreases its momentum as it goes up

Question 5

What is elastic collision

Answer 5

When no kinetic energy is lost it gained

Question 6

What is a crumple zone

Answer 6

Front and end of a car to lessen impact force . Increase impact time

Question 7

Equation for acceleration

Answer 7

Change in acceleration
——–/————
Time taken

Question 8

Equation force mass acceleration

Answer 8

Force =mass x acceleration

Question 9

Five momentum time

Answer 9

Force = change of momentum
——————-
Time taken

Question 10

What happens in an impact when moving object is speeded up

Answer 10

Momentum increases

Question 11

Momentum equation

Answer 11

Mass x velocity

Question 12

What happens to momentum in ana explosion

Answer 12

Is conserved objects move off in different directions
Positive direction right
Negative direction left

Question 13

Thinking distance

Answer 13

How far car moves when driver suddenly sees a new obstacle and takes time to react to new situation before taking action

Question 14

How is thinking distance related to speed and reaction time

Answer 14

Longer reaction time longer thinking distance and greater speed longer thinking distance

Question 15

Braking distance

Answer 15

How far car travels after driver pushes the brakes and brings it to a stop

Question 16

Factors effecting thinking distance

Answer 16

Tiredness , influence of drugs and alcahol that slow reaction time

Question 17

Factors effecting braking distance

Answer 17

Mass of vehicle , breaking force applied , velocity the vehicle travels at

Question 18

Difference between scalar and vector

Answer 18

Vector is a quantity which has size and direction

Scalar has no direction and is only size

Question 19

How does heavy rain affect cars stopping distance

Answer 19

Increased as car cannot break without skidding , lowers breaking force and increased braking distance

Question 20

Inelastic collision

Answer 20

2 objects collide and stick together e.g two railway trucks

Question 21

Elastic colisión example

Answer 21

Colission between molecules in a gas

Question 22

When is momentum not conserved

Answer 22

In a collision when external forces act on the object

Question 23

Kinetic energy

Answer 23

Kinetic energy = 0.5 mass x velocity squared

Question 24

Unit for momentum

Answer 24

Kg m/s

Question 25

Impulse

Answer 25

Force x time

Question 26

What happens to momentum

Answer 26

Stays the same providing no external forces act

Question 27

Partially elastic collision

Answer 27

Where object looses some kinetic energy

Question 28

Elastic behaviour

Answer 28

Ability of a material to return to original shape after forces causing deformation have been removed

Question 29

Hookes law

Answer 29

Extension of a spring is proportional to force up to the elastic limit

Question 30

Why do rubber bands not demonstrate hooks law

Answer 30

At beginning the band is stiff and doesn't stretch much but after it softens

Question 31

Why do sky divers bend legs when landing

Answer 31

Landing requires rapid de acceleration so sky divers bend legs so landing takes longer and reduces the force that if the force was large it could break their bones . Bending legs makes landing take longer and reduces force

Question 32

Stopping distance

Answer 32

Sum of thinking and breaking distance

Question 33

Why does a trolley accelerate

Answer 33

It's weight provides a force to accelerate it

Question 34

What does friction do to speed

Answer 34

Friction increases with speed and leads to a smaller resultant force on the object and therefore a smaller acceleration

Question 35

Instantaneous speed

Answer 35

Speed over a short amount of time Distance covered -------------- Small time interval

Question 36

Force

Answer 36

Mass x acceleration

Question 37

What happens if balance forces act on an object

Answer 37

Moves at a constant speed or stays stationary

Question 38

What is moment

Answer 38

Measuring of a forces turning effect

Question 39

Moment equation

Answer 39

Moment = force x perpendicular distance to line of action of action

Question 40

What must moment be for an object to be in equilibrium

Answer 40

Moment must be equal on both side

Question 41

How to change an objects speed

Answer 41

Unbalanced force must act on it the greater the size the faster the object will speed up or slow down

Question 42

What is a force

Answer 42

A push or a pull

Question 43

What does the gravitation. Field do

Answer 43

Accelerates falling objects . Frictional forces increase until they balance gravitational force

Question 44

Weight

Answer 44

= mass x gravitational field strength

Question 45

Centre of gravity

Answer 45

Where the weight force acts

Question 46

Elastic limit

Answer 46

The limit when the shape will change permanently and not return to original length

Question 47

What is moment measured in

Answer 47

Newton meters

Question 48

What is momentum

Answer 48

A force possessed by masses in motion, a measure of how difficult it is to stop something from moving

Question 49

What is moment

Answer 49

Forces that make objects turn around a fixed point

Question 50

Why do passengers wear seat belts

Answer 50

So the reduced deacceleration applies to the passengers body otherwise they will come into contact quickly with another person or part of the car causing a large force to act on them

Question 51

How to find cemetery of gravity on a regular shape

Answer 51

Located where lines of symmetry cross

Question 52

How to find centre of gravity on an irregular shape

Answer 52

The point of suspension is a pivot point . Shape will not come to rest until it is balance and the centre of gravity is just below the pivot . A plumb line is hung from the pivot point so a like can be drawn perpendicularly from the pivot . The centre of gravity is somewhere along this line . This procedure is repeated suspending the card from a different pivot point and the centre of gravity will be where the two lines cross

Question 53

What affects an objects stability

Answer 53

Low centre of gravity and broad base