EK 1001 Physics Kinematics "harder questions" 54-61

[GRod18]

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all of these questions are all based off this single scenario, it is giving me quite a bit of trouble. If anyone could answer a few of these for me in non EK terms I would appreciate it 😛

A particle moving at 5 m/s reverses its direction in 1 s to move at 5 m/s in the opposite direction. If its acceleration is constant.

What is its magnitude of its acceleration?

Answer: 10m/s^2 (ok I know this one)

What is its displacement from its original position at 1s?

Answer: 0 m

What distance does it travel?

Answer: 2.5 m

What is its speed at 0.5 s?

Answer: 0 m/s

What is its displacement at 0.5 seconds?
Answer : 1.25 m

 

[Marathon Doctor]

The key to this problem is to define which Velocity is (+).

- Lets say that Vo (initial velocity) is positive. a= (V-Vo)/t= -10m/s^2

- Now, use the "a" to find the displacement using x= Vot + 1/2 at^2 (dont forget the negative sign for acceleration)

- Distance = (Displacement in 0.5 sec) * 2

- Use V = Vo+at to find the velocity at 0.5 sec

 

[GRod18]

thank you so much!

That {displacement in 0.5 sec} x 2 clears it up. Sometimes, EK's explanation is lacking, but for these I think it tried to explain a little bit more than necessary and makes it confusing lol..