Question

Two rollerbladers face each other and stand at rest on a flat parking lot. Tracey has a mass of 32 kg, and Jonas has a mass of 45 kg. When they push off against one another, Jonas acquires a speed of 0.80 m/s .
What is Tracey's speed?
Express your answer to two significant figures and include the appropriate units.

Answer 1

Mass of Tracey M1 = 32 kg

Mass of Jonas M2 = 45 kg

Initially both were at rest

so V1i = V2i =0

after pushing each other Jonas speed V2f = 0.80 m/s

we need to find out final speed of Tracy

Here we can use momentum conservation as no external force is acting here

M1V1i + M2V2i = M1V1f + M2V2f

32(0) + 45(0) = 32 V1f + 45(0.80)

0 = 32 V1f + 36

-36 = 32 V1f

V1f = - 1.125 m/s

negative sign shows that Tracy will move opposite to the Jonas

so answer in two significant figure would be

V1f = 1.1 m/s

Answer 2

 = 0.77 m/s hope this helps