Physics Question (Help Please)

[k.rotelli]

The roller coaster car shown in the figure starts from a standstill position at point Q.

illustration

Ignoring friction, what is the ratio between the velocities of the roller coaster car at point S and at point R? A: 1/√2
B: 2
C: √2
D: 1/2
E: 1/4

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[Juliette]

Hi!

We are starting from a standing position meaning u = 0

For point R:
v² = u² + 2as
V² = 0 + 2 * 10 * 50
v = 10 * square root of 10

For point S u = 10 * square root of 10
v² = (10 square root of 10)² + 2 * (-10) * 25
v = 10 square root of 5

R : S
10 square root of 10 : 10 square root of 5
square root of 10 : square root of 5
square root of 2 : 1

so the ratio of S/R = 1/square root of 2

Hope this helps!