Motion

Question 1

what is the instantaneous velocity

Answer 1

the velocity at a given instant in time

Question 2

what is the average velocity

Answer 2

the total displacement divided by the total time taken

Question 3

how to find the instantaneous velocity from a curved displacement-time graph

Answer 3

draw a tangent to the point then find its gradient

Question 4

whats the velocity of an object bouncing at the very top

Answer 4

0m/s

Question 5

whats the acceleration of a bouncing object

Answer 5

g (-9.81m/s^2)

Question 6

experiment to determin g

Answer 6

1. set up a steel ball and trapdoor
2. record ball height
3. open door and time how long it takes to drop (can use pressure plate and electronic timer)
4. record average of three attempts
5. measure time form a range of heights
6. plot a graph of hight against time^2 (should be straight)
7. calculate g (its the gradient * 2)

Question 7

what is lift

Answer 7

it’s the upward force caused by collisions with air particles on the underside of a wing

Question 8

how does a plane create lift

Answer 8

as it moves forward it pushes air particles down. this causes an equal and opposite upward force on the wings

Question 9

how are wings shaped and why

Answer 9

angled top maximise the amount of air it can push down.

curved and smooth to reduce drag

Question 10

what is friction

Answer 10

the resistance to motion due to contact forces

Question 11

what does friction do

Answer 11

it converts kinetic energy into other types (mostly thermal)

Question 12

what is drag

Answer 12

it’s a frictional force caused by motion in liquids and gases caused by collisions with particles.

Question 13

factors affecting drag

Answer 13

speed of an object
the shape of the object (how streamlined it is)
surface area

Question 14

what is air resistance

Answer 14

the frictional force (drag) opposing the motion of an object travelling through air

Question 15

how is terminal velocity reached

Answer 15

weight stays constant so the downward force doesn’t change. as the objects speed increases the drag increases until it equals the weight. when this occurs the object is at terminal velocity

Question 16

why do parachutes slow your fall

Answer 16

the increased surface area increases air resistance. the resistive force is now greater than the wight. this causes deceleration. the speed decreases and so does the drag until its equal to the weight again. this is at a new slower terminal velocity

Question 17

factors affecting reaction time

Answer 17

drugs/alcohol
fatigue
distractions

Question 18

how does the velocity of a vehicle change the stopping distance

Answer 18

the thinking distance increase linearly with the velocity and the braking distance is proportional to the velocity^2

Question 19

an important thing about projectile motion?

Answer 19

the horizontal and vertical components are independent meaning they are solved separately

Question 20

what forces act on projectiles

Answer 20

only gravity. the vertical acceleration is always 9.81m/s^2 and the horizontal is always 0

Question 21

What’s Newton’s first law

Answer 21

the velocity of an object won’t change unless a resultant force acts upon it

Question 22

What’s Newton’s second law

Answer 22

force and acceleration are directly proportional

Question 23

What’s Newton’s third law

Answer 23

when a force acts on an object it applies an equal and opposite force back (for every action there is an equal and opposite reaction)

Question 24

what is the impulse of an object?

Answer 24

its change in momentum

Question 25

what is the conservation of momentum?

Answer 25

momentum can not be created or destroyed so momentum before a collision = momentum after a collision

Question 26

difference between elastic and inelastic collisions

Answer 26

elastic collisions conserve kinetic energy and momentum. inelastic collisions only conserve momentum because some energy is dissipated as thermal or other energy

Question 27

what type of collision is an explosion

Answer 27

its a reverse collision. it is an inelastic process as kinetic energy is not conserved. the kinetic energy comes from the internal energy

Question 28

what are some safety features in cars?

Answer 28

airbags crumple zones seat belts

Question 29

how do safety features of a car work

Answer 29

they absorb some of the kinetic energy from a collision. they increase the time taken for the change in momentum to happen, reducing the force

Question 30

definition of a radian

Answer 30

the angle between two radii of a circle that are connected with an arc equal to the radii's length

Question 31

what is the angular speed

Answer 31

a measure of how quickly an object's rotating. the change in angle divided by the change in time

Question 32

whats the period in circular motion

Answer 32

the amount of time taken for one resolution

Question 33

whats the frequency in circular motion

Answer 33

the number of times it goes around the circle per second

Question 34

why is an object in circular motion always accelerating

Answer 34

acceleration is the change in direction or magnitude of velocity. in a circle, the direction is always changing so an object is always accelerating and its always towards the centre of the circle

Question 35

why is the acceleration of circular motion towards the centre

Answer 35

the change in velocity is always towards the centre. this is called centripetal acceleration

Question 36

what is centripetal force

Answer 36

any force that causes circular motion. the larger the force the smaller the circle. it's always perpendicular to instantaneous velocity

Question 37

define simple harmonic motion

Answer 37

any motion where the acceleration is directed towards a fixed point and is directly proportional to the negative of the displacement

Question 38

whats the gradient of an acceleration-displacement graph

Answer 38

the angular frequency (notation- ω) squared by -1. to get the angular frequency square root the (gradient * -1) gradient = -1(ω^2)

Question 39

for simple harmonic motion how do acceleration-time graphs and displacement-time graphs differ

Answer 39

they are a reflection in the X-axis of each other.

Question 40

how does the GPE, KE and EPE change in a pendulum simple harmonic system

Answer 40

at the centre of the oscillation, KE is at a maximum and GPE and EPE are at a minimum. at the top of the oscillation, the GPE and EPE are at a maximum and KE is 0.

Question 41

what is a damping force

Answer 41

and force opposing motion (frictional forces)

Question 42

what happens when an oscillation is damped

Answer 42

the amplitude decreases. the period and frequency remain the same

Question 43

what are under-damping and over-damping

Answer 43

under-damping is when the effects of damping are so minor it would take a long time to see a decrease in amplitude over-damping causes no oscillations. the object just returns to equilibrium slowly. when the object returns to equilibrium as quickly as possible this is critical-damping

Question 44

how can you find a resonance curve

Answer 44

plotting a graph of amplitude against frequency

Question 45

how does damping affect the resonance curve

Answer 45

the greater the damping effect is the flatter the resonance curve is

Question 46

when does resonance occur

Answer 46

when the applied frequency and natural frequency are similar