Topic 10 (mechanics)

Question 1

force diagram

Answer 1

diagram showing all the forces acting on an object

• each force shown by an arrow pointing in direction in which the force acts
• used to model problems involving forces

Question 2

force labels

Answer 2

R: normal reaction of the rough horizontal plane on the block (acting upwards)

P: force pulling the block (acting to the right)

F: resistive force due to friction (acting to the left)

W: weight of the block (acting downwards)

Question 3

weight

Answer 3

-force between any object and the earth
-force due to gravity acting on an object = weight of the object and it acts vertically downwards
-body falling freely experiences acceleration of g = 9.8 (metres per second squared)
F=ma can write formulae for weight of a body mass, m
W= mg (N)

Question 4

Newton’s first law of motion

Answer 4

• states an object will remain at rest or keep moving with a constant velocity unless a resultant force is applied to it
• moving particle will remain in equilibrium as long as the resultant force in all directions is 0
• particle doesn’t have to be stationary to be in equilibrium it could be moving with a constant velocity

Question 5

tension

Answer 5

-string is attached to a particle and pulled vertically upwards so the particle moves with constant velocity (1m/s)
-particle travelling with constant velocity and so is in equilibrium the forces must balance
T - tension
tension forces in the string is a pulling force, these forces in the diagram are equal in magnitude and the box in equilibrium

T-W = 0
T=W

Question 6

Thrust

Answer 6

• a particle being pushed vertically upwards by a rod so that the particle moves with a constant velocity of 5m/s
• particle is travelling with a constant velocity and so is in equilibrium the forces balance

T = thrust
when a rod is pushed (compressed) the force is a thrust force)
-forces in diagram are equal in magnitude and the box is in equilibrium

R |T-W = 0
T=W

Question 7

RESOLVING FORCES

Answer 7

resolving vertically R (up arrow) R-W =0
resolving horizontally R(->) P-F = 0

resolve forces in direction of motion and perpendicular to this direction

Question 8

When the particle is in equilibrium the…

Answer 8

Forces balance
resultant force is zero
particle could be stationary
particle could move with constant velocity

resultant force is the combined effect of all the forces
F1 + F2 + F3 act on an object the resultant force is
R = F1 + F2 + F3

Question 9

kinematics

Answer 9

study of motion(using Suvat)

Question 10

dynamics

Answer 10

study of motion produced by forces

Question 11

newtons second law

Answer 11

states the resultant force acting on a particle is equal to the product of the mass of the particle and its acceleration
if resultant force FN acts on an object with mass mkg giving it an acceleration of a m/s squared then:

F=ma

Question 12

connected particles

Answer 12

• all parts of system moving in same straight line = can consider whole system as a single particle or consider each particle separately
• if parts are moving in different direction = consider each particle separately (must take care to include all forces acting upon them)

Question 13

newtons third law

Answer 13

states for every action there is an equal and opposite reaction

if particle A exerts force on particle B B will exert an equal and opposite force on A forces will be equal in magnitude and in opposite direction

Question 14

systems:

Answer 14

• if all parts of system moving in same straight line =
• consider whole system as a single particle or consider the each particle separately
• if parts moving in different directions =
• consider each particle separately
• must take care to include all forces acting upon them

-particles must remain in contact or be connected by an inextensible rod or string to be considered as a single particle