Motion & Newton's Laws & Energy

Question 1

what is v

Answer 1

change in position over time (s/t)

Question 2

what is speed

Answer 2

how fast the distance is changing every sec

Question 3

what is acceleration

Answer 3

how fast the velocity is changing e.g. Vf-Vi/t

Question 4

what is s

Answer 4

straight line distance from start point to end point

s= ut + 1/2(at^2)

Question 5

what do vectors need

Answer 5

scalar & direction e.g. 15m <– = -15

Question 6

what is newton’s 1st law

Answer 6

silk table cloth - body will remain at rest / move with constant v unless acted on by a resultant force

Question 7

what is newton’s 2nd law

Answer 7

F = ma e.g. the resultant force on an object is equal to the rate of change of it’s momentum

Question 8

what is newton’s 3rd law

Answer 8

equal & opposite force

Question 9

what is the difference between driving & frictional forces

Answer 9

driving is pushing the object and is +ve, while frictional is resisting it and is -ve

Question 10

where do gravitational fields point

Answer 10

directly toward the centre of massw

Question 11

how is gravity measured (units)

Answer 11

N/kg or m/s2

Question 12

what is kinetic energy

Answer 12

E = 1/2(mv^2)

Question 13

what is gravitational energy

Answer 13

E = mgh

Question 14

what is work energy

Answer 14

W = Fs

Question 15

what is torque

Answer 15

tao (t) = Fr

Question 16

what are the principles of projectile motion

Answer 16

• symmetrical
• v = 0 at max height
• v for vertical component
• kinetic energy than gravitational energy

Question 17

what are the principles of circular motion

Answer 17

a = v^2/r
so F = m(v^2/r)
use trig to work out tension

Question 18

what is the formula for gravitational field strength on earth

Answer 18

g = (G x m)/r^2
where m = planet mass, r = distance from centre of mass

Question 19

what is the relationship between gravitational strength & distance r

Answer 19

being further away (big r) reduces g

Question 20

what is the relationship between r & F in torque

Answer 20

inverse, harder to push a door near it’s pivot point, easier further out

Question 21

what is the formula for elastic energy

Answer 21

E = 1/2* (kx^2)
where x = compression, k = spring constant (N/m)

Question 22

what is momentum and can newton’s 3rd law apply

Answer 22

p = m*v

yes

Question 23

what is the formula for impulse momentum

Answer 23

change in p = net F x change in t,

where p = pfinal - pinital
- so it can be -ve

Question 24

can net force be negative

Answer 24

yes when the object comes to a stop

Question 25

what is potential energy & it’s diff. to kinetic

Answer 25

energy stored by a field e.g. gravitational, electric or magnetic

e.g. not kinetic because these are particles moving around

Question 26

what happens when 2 gasses are heated to produce water, gas and energy e.g. CH4 + O2 –> H2O + CO2 + energy

Answer 26

greater PE –> lower PE, more KE and radiation

Question 27

is radiant energy (light/warmth) kinetic or potential?

Answer 27

both

Question 28

what is the formula for power

Answer 28

W/change in time

Question 29

what is the significance of gravitational fields for an object in free fall

Answer 29

acceleration = magnitude of gravity

Question 30

what is the formula for tension

Answer 30

a = sum of forces/mass of object

gravity is a negative forcce because tension is always pulling, while gravity is pushing