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GCSE Questions: Momentum

Q5. Thea investigates collisions of trolleys on a horizontal airtrack.

 

 

Trolley A has a mass of 2kg - - - - - - - - - Trolley B has a mass of 2.5kg

(a) Write down the two quantities involved with motion which are conserved during an elastic collision.

momentum and kinetic energy

[2 marks]

(b)

(i) Calculate the momentum of each trolley.

Trolley A

p = mv

pA = 2 x 4.2

pA = 8.4 kg m/s

Trolley B

p = mv

pB = 2.5 x 2.7

pB= 6.75 kg m/s

[4 marks]

(ii) The two trolleys collide and stick together after the collision.

Use your answers to (b)(i) to calculate the speed of the combined trolleys after the collision.

Record your answer to 2 significant figures

Σp (before collision) =  Σp (after collision)

pA + pB = pA+B

pA+B = 8.4 + 6.75 = 15.15

pA+B = mA+B x vA+B

15.15 = (2 + 2.5) vA+B

vA+B = 15.15/4.5

vA+B = 3.367

vA+B = 3.4 m/s

Just rounding a wrong answer to 2 sf correctly got you a mark!

So if you have no clue how to do a question make something up then correctly round an answer to the number of sig figs they ask for...

It may get you a mark!

[4 marks]

[10 Marks TOTAL]