Further motion concepts

Question 1

What is the equation for momentum?

Answer 1

momentum (p) (kg m/s) = mass (m) (kg) x velocity (v) (m/s)

p = mv (therefore momentum is the product of mass and velocity)

Question 2

What is the equation linking momentum and resultant forces?

Answer 2

resultant force (f) (N) = change in momentum (kg m/s) / time for the change (t) (s).

Question 3

What is the law of conservation of momentum?

Answer 3

Total momentum before an interaction = total momentum after an interaction. (By convention, the momentum in one direction is considered to be positive, whilst the momentum in the opposite direction is considered to be negative.)

Question 4

What are elastic collisions?

Answer 4

Kinetic energy is is only conserved in elastic collisions, where the total kinetic energy before the collision is the same as the total kinetic energy after the collision. However, very few collisions are truly elastic as most involve some kinetic energy loss which is transformed int other forms of energy, such as the strain energy that deforms an object, or he and sound - these collisions are called inelastic collisions.

Question 5

What are the symbols involved in kinematic equations?

Answer 5

x = distance travelled (in m)
u = initial velocity of the object (in m/s)
v = final velocity of the object (in m/s)
a = acceleration of the object (in m/s^2)
t = time of the motion (in s)

Question 6

What are the 4 kinematic equations?

Answer 6

v = u + at
x = ( u + v / 2 ) x t 
x = ut + 1/2at^2
v^2 = u^2 + 2ax
***when objects are moving by falling due to the Earth's gravitational field, the symbol g is used instead of a, and the value of g remains constant at 10 m/s^2.

Question 7

What is a turning force?

Answer 7

When a force (f) acts at a distance (d) away from the centre of a pivot (such as a spanner turning a nut), the force exerts a turning effect on the pivot, called a turning force.

Question 8

What is the force that acts on the pivot and its equation?

Answer 8

The turning force that acts on the pivot is called a moment and it is calculated bu using -
moment (M) = force (F) x distance (d)
M=Fd where d is the distance of the force away from the axis of rotation of the pivot. The units of a moment are Nm.

Question 9

What does the principal of moments states?

Answer 9

The principal of moments states that if a beam is balanced, then the sum of the clockwise moments must equal the sum of the anticlockwise moments around a point.