mechanics (only non maths topics)

Question 1

newtons 1st law of motion

Answer 1

the velocity of an object will not change unless a resultant force acts on it

Question 2

newtons 2nd law motion

Answer 2

Force ∝ rate of change of momentum
F = Δ(mv)/Δt

or (F=ma) (dont put this one as the asnwer tho)

Question 3

newstons 3rd law of motion

Answer 3

if object A exertes a force on object B, then pbject B exerts a equal but opposite force on object A

Question 4

the pair of forces in newtons 3rd law are always the ______ ______

give an example and one commenly thought of example that is not actually newtons 3rd law

Answer 4

same type

A) pushing against water

b) a book on a table is not an example of newtons 3rd law a the 2 forces acting upon teh book are not the same

Question 5

momentum equation and units

Answer 5

momentum = mass x velocity
ρ = m x v (kgms^-1)

Question 6

is momentum a scaler or a vector quantity

Answer 6

vector

Question 7

assuming no external forces act, momentum is _______

Answer 7

conserved

Question 8

what is a elastic collision

Answer 8

a collision where momentum and Ek is conserved (therefore NO enegy is dissipated as heat , sound ect)

Question 9

what is a inelastic colision

Answer 9

a collision where Ek is not conserved (e.g therefore enegy IS dissipated as heat , sound ect)

tho momentum is conserved

Question 10

in both elastic and inelastic what is always conserved

Answer 10

momentum

Question 11

what is impulse

Answer 11

change of momentum

Question 12

rearage the newtons second law equaiton to find impulse and give the units

Answer 12

F = Δ(mv)/Δt
Ft = Δ(mv) (just assuming Δt is t as you would in any suvat equation)
Ft = mv - mu where v is final valocity and mu is initioal velocity)
units = Ns

Question 13

what is impulse defined as in terms of force and time

Answer 13

F x t

Question 14

what is the area under a force x time graph

Answer 14

impulse

Question 15

work done equation and units

Answer 15

wd=f x d jules(J)

(the force needs to be fixed) (can be constent or a avarge)

Question 16

defonition of a jule

Answer 16

one jule is the work done when a force of 1 newton moves an object through a distance of 1 meter

Question 17

what is the area under a force displacment diagram

Answer 17

word done

Question 18

gice the 2 equations of power for mechanics and the unit

give 1 more power equation

Answer 18

power = wd/t therefore power = workdone per second

power = F x V

units = w

power=E/t

Question 19

1 watt is ___ _____ __ _____

Answer 19

1 juel per second

Question 20

exam questions (1m):
there are 2 sample wires but the second one has 3 x Lenth and 1/2 the diamitor what is the youngs modules of the new meterial in terms of E (youngs modules of the origenal meterial)

Answer 20

E
the youngs modules is a propity of a meterial thus not effected by the changing of dimensions

Question 21

what word often siginifiers within a question that you are ment to use momentem equation within the question

Answer 21

collision

(and if they dont state weather the collision is inelastic or elastic)

Question 22

what do 2 forces need to be to be newtons 3rd law pair foces (3)

Answer 22

• the forces need to have the same magnatude
• the forces need to be of the same type
• the forces need to act on 2 diffrent objects NOT the name on

Question 23

GPE equation

Answer 23

mgh

Question 24

interactions A:
a pellet hits a block and is imbeded,

interaction B:
a pellet hits a block and bounces back

in wich interaction does the block have the greatest v after the interaction

Answer 24

interaction B
because

ρ is a vector.
since the pellet and the block hgas the same momentum before the interaction but after the interaction the pellet has negetive vlocity.
as ρ is conserved.
after the interaction teh block must have greater ρ.
since the blocks mass stays the same.
the the v i fthe block must be greater to compensate for the negetive velocity of the pellet.

ρ after = ρ before
m1u1+m2u2=m1v1+m2v2
m1u1+m2u2 does not change
m1v1 decreases
so
m2v2 must increase

Question 25

what is an elastic collision

Answer 25

where ρ and Ek is conserved

Question 26

what is a inelastic collision

Answer 26

where only ρ is conserved and NOT Ek