6. Further Mechanics

Question 1

What is an impulse?

Answer 1

• The change in momentum.

- given by Ft=p

Question 2

Derive impulse from newtons second law?

Answer 2

F=ma
a=Δv/Δt

∴ F=Δ(mv)/Δt
∴ FΔt = Δmv = Δp

Question 3

How would you go about conserving momentum in two dimensions?

Answer 3

Resolve the motion into components (along the perpendicular axis).

Question 4

What is the difference between an elastic and inelastic collision?

Answer 4

Elastic: kinetic energy is conserved.

Inelastic: kinetic energy is not conserved (converted into/transferred from other forms).

Question 5

Is an explosion elastic or inelastic?

Answer 5

Inelastic.

As the kinetic energy after is greater than before.

Question 6

Derive Eₖ = p²/2m using formulas for kinetic energy and momentum.

Answer 6

Eₖ = ½mv²
p = mv

v= p/m
∴ Eₖ = ½m(p²/m²)
= ½(p²/m)
= p²/2m

Question 7

What is a radian?

Answer 7

• The angle in the sector of a circle when the arc length of that sector is equal to the radius of the circle.

Question 8

What is angular displacement?

Answer 8

• The angle turned through in a given direction…

- in radians or degrees.

Question 9

What is angular velocity?

Answer 9

• The angle an object moves through per unit time.

Question 10

How do you calculate the angular velocity from the angular displacement?

Answer 10

Δθ/Δt