Q 3 Revisited

Why did the two different methods produce different results?

The question was inconsistent!

Initial momentum was 0.117 kgms-1

One of the momentum vectors was at an angle of 50 degrees.

The other vector was at 90 degrees to that one.

Now the triangle is fixed! All quantities can be calculated. There is no freedom to make up results.

Calculate what the velocities should have been.

Initial momentum was 0.117 kgms-1

50 degrees.

90 degrees

The masses have a mass of 0.065 kg.

40 degrees

Trigonometry.Initial momentum was 0.117 kgms-1

50 degrees.

90 degrees

Sin 40 = p2 / 0.117

p2 = 0.117 x sin 40

= 0.0752 kgms-1

40 degreesp2 p1

Cos 40 = p1 / 0.117

p1 = 0.117 x cos 40

= 0.0896 kgms-1

Pythagoras : sqrt of (0.07522 + 0.08962) = 0.11697 – Agrees!!

Velocities

p2 = 0.0752 kgms-1 = 0.065kg x V2

V2 = p2 / 0.065 = 1.156 ms-1 = 1.2 ms-1 (2 s.f)

p1 = 0.0896 kgms-1 = 0.065kg x V1

V1 = p1 / 0.065 = 1.378 ms-1 = 1.4 ms-1 (2 s.f)