Chapter 7 - momentum and newton's laws

Question 1

state Newton’s first law

Answer 1

“an object will remain at rest or continue to move at a constant velocity unless acted on by a resultant force”

Question 2

what must have happened if an object’s velocity or direction changes

Answer 2

there must be a resultant force

Question 3

state newton’s 3rd law

Answer 3

“when 2 objects interact they exert equal and opposite forces on each other”

Question 4

how to check if its a diagram of newton’s 3rd law

Answer 4

• you will never see the forces acting on the same object if its newton’s third law
• if its newton’s third law, both forces will be of the same type

Question 5

what are the 4 fundamental types of interaction

Answer 5

electrostatic, weak nuclear, strong nuclear, gravitational

Question 6

momentum equation

Answer 6

p (kgms^1)(Ns) = m(kg) v(ms^1)

Question 7

what type of quantity is momentum

Answer 7

a vector quantity

Question 8

what is the principle of conservation of momentum

Answer 8

“for a system of interacting objects the total momentum in a specified remains constant providing there are no external forces”

Question 9

ways of investigating momentum

Answer 9

trolleys or objects on an air track can be sent at a set speed down a track
their velocity can be measured using light gates at different points on the track
if the mass of the object/trolley is known then the momentum can be calculated

Question 10

what is the definition for an elastic collision

Answer 10

a collision where both total energy and kinetic energy is conserved

Question 11

what is the definition for an inelastic collision

Answer 11

a collision where total energy but not kinetic energy is conserved

Question 12

similarities and differences between elastic and inelastic collisions

Answer 12

in both momentum and total energy is conserved
in elastic kinetic energy is conserved
in both the impulse experienced by both objects is equal

Question 13

state Newton’s second law

Answer 13

“the net force acting on an object is directly proportional to the rate of change of its momentum and is in the same direction”

Question 14

what is the equation for Newton’s second law

Answer 14

F = delta P / delta T

Question 15

what is the special case (and relevant equation) of newton’s second law

Answer 15

when mass is constant it can be thought of as F = MA

Question 16

when is impulse used

Answer 16

its often used to analyse situations when forces accelerate or decelerate an object over time

Question 17

what is the equation for impulse and which of Newton’s laws does it link to

Answer 17

delta p = change in momentum = impulse
delta p = F x delta t
it links to the equation for Newton's second law
measured in (kgms^-1) or (Ns)

Question 18

what is the alternative equation for impulse

Answer 18

delta p = MV - MU

Question 19

what does impulse represent

Answer 19

the area under a force-time graph

Question 20

how can the concept of conservation of momentum be extended to include collisions in 2 dimensions

Answer 20

momentum in the X direction must be conserved

momentum in the Y direction must be conserved

Question 21

what is the exit angle when two objects of the same mass collide obliquely

Answer 21

90 degrees

Question 22

what is the equal and opposite force to the weight of an object

Answer 22

the attraction of the earth to the object