Mechanics

Question 1

what is a projectile

Answer 1

an object where the only force acting on it is its weight (assuming air resistance has no effect)

Question 2

is air resistance is negligible what does this mean for forces on the object

Answer 2

there is no horizontal forces acting on the object so the horizontal velocity is constant throughout.

Question 3

how do you calculate horizontal displacement

Answer 3

horizontal velocity multipled by time in the air

Question 4

what is the vertical component in a projectile

Answer 4

as weight is the only thing affecting it the acceleration is due to gravity (9.81) gain every second

Question 5

how can you calculate vertical values on a projectile

Answer 5

using SUVAT

Question 6

how does air resistance change the trajectory of a projectile

Answer 6

the horizontal velocity slowly starts to decrease (as there’s air resistance), therefore not travel as far
vertical velocity will gain speed slower

Question 7

what is friction

Answer 7

the force that opposes motion, turning kinetic energy into thermal energy and can never speed things up or start them moving

Question 8

what are the 2 types of friction

Answer 8

contact friction-between 2 solid surfaces
fluid friction- called drag between liquids or gasses

Question 9

what factors affect drag

Answer 9

increases when:
larger surface area
larger speed
larger density

Question 10

what is lift

Answer 10

its an upwards force happening when moving through a fluid, causing the fluid its moving through to change direction

Question 11

what directions do lift and drag act in

Answer 11

lift acts perpendicular to direction of fluid flow and drag acts parallel to it

Question 12

what 3 things cause lift

Answer 12

if the wing diverts air downwards
impact of air on the wing (newtons 3rd law)
Bernoullis principle

Question 13

what is Bernoullis principle

Answer 13

faster air means less pressure so air travelling over the top of the wing travels faster so more pressure is below the wing

Question 14

what is terminal speed

Answer 14

when the frictional forces on an object equal the driving force on an object. there’s is no resultant force and now travels at a constant velocity

Question 15

what is linear momentum

Answer 15

the product of an object’s mass and velocity
its a vector quantity

Question 16

what’s the principle on conservation of momentum

Answer 16

the total momentum before the collision is equal to the total momentum after the collision provided there’s no external forces acting on the object

Question 17

how does conservation of momentum effect explosions

Answer 17

the momentum before is 0, so it has to be 0 after the explosion. this is achieved by loads of fragments flying off in different directions

Question 18

what is an elastic collision

Answer 18

where momentum is conserved as well as kinetic energy.
eg. collisions of air molecules

Question 19

what is an inelastic collision

Answer 19

where momentum is conserved but kinetic energy isn’t conserved mostly lost through heat and sound

Question 20

what is a perfectly inelastic collision

Answer 20

where the colliding objects stick together whether they are still moving or not. this is the maximum amount of kinetic energy that can be lost while still conserving momentum
eg. blue tac falling onto a table

Question 21

what happens to the momentum of a single object in a collision

Answer 21

the momentum of the single object will change

Question 22

what is change in momentum

Answer 22

force is equal to the rate of change of momentum

Question 23

what is impulse

Answer 23

the product of force and time/ equal to change in momentum

Question 24

how do you find impulse from a graph

Answer 24

the area under a force time graph

Question 25

how do impulse and change in momentum have practical uses in cars

Answer 25

crumple zones-by increasing the impact time the force is smaller airbags- prevent your head from hitting a hard surface and decelerating quickly seatbelts

Question 26

how do impulse and change in momentum have practical uses in sport

Answer 26

in sports like tennis and golf you want the ball to have the greatest velocity. apply more force use smaller mass increase contact time

Question 27

what is work

Answer 27

work is done when energy transforms from one form to another

Question 28

what 2 things effect work done

Answer 28

the greater the force or the distance the object moved the more work needed to be done

Question 29

how much work does a satellite do

Answer 29

none, the force of gravity is perpendicular to the force of motion so it cancels out

Question 30

how can work be found on a graph

Answer 30

the area under a force against distance graph

Question 31

what is power

Answer 31

the rate of doing work

Question 32

what is the principle of conservation of energy

Answer 32

energy cannot be created or destroyed but can be transferred from one form to another. the total amount of energy in a closed system will not change

Question 33

what is efficiency

Answer 33

a way of quantifying how much energy is being converted into useful energy, usually expressed as a percentage

Question 34

when would you use SUVAT

Answer 34

when acceleration is uniform

Question 35

what are key features of a displacement time graph

Answer 35

straight line gradient=velocity curved line= acceleration (find tangents for velocity)

Question 36

what do different gradients mean on a displacement time graph

Answer 36

steep gradient= high velocity shallow gradient= low velocity negative gradient= travelling backwards horizontal gradient= stationary

Question 37

how do you find average velocity on a displacement time graph

Answer 37

if the line is very curvy, draw a line of best fit and calculate the gradient from that

Question 38

what are the key features of a velocity time graph

Answer 38

gradient= acceleration area under graph= change in displacement

Question 39

what do different gradients mean on a velocity time graph

Answer 39

steep= high acceleration shallow= low acceleration horizontal= constant velocity negative= deceleration

Question 40

what does a curved line mean on a velocity time graph

Answer 40

the curve means changing acceleration

Question 41

what is the key feature on an acceleration time graph

Answer 41

area under the graph= change in velocity above x-axis=positive change in velocity below x-axis= negative change in velocity (slowing down)

Question 42

what is newtons first law

Answer 42

if there is no resultant force acting on an object its either at rest or traveling at a constant velocity

Question 43

what is newtons second law

Answer 43

F=ma

Question 44

what is newtons third law

Answer 44

if object A exerts a force on object B, object B exerts and equal and opposite force on object A

Question 45

what is meant by freefall

Answer 45

the object only has weight acting on it

Question 46

why do all objects fall at g

Answer 46

with no air resistance all objects would accelerate at the same rate and therefore hit the ground at the same time

Question 47

What is a scalar

Answer 47

A quantity that only has magnitude

Question 48

What is a vector

Answer 48

A quantity that has both direction and magnitude

Question 49

What are 3 examples of scalar quantities

Answer 49

Time Speed Distance

Question 50

What are 3 examples of vector quantities

Answer 50

Displacement Velocity Force