Mechanics theories.....need help brushing up (1 Viewer)

[RideTheLightnin]

hey guys, im having difficulty on some mechanics concepts
I dont do physics so please pardon my lack of knowledge....
1. How do you work out what the starting equation is? Like if its a straight line do you just write a=kv? and if slowing down a=-kv?
2. Is retardation just negative acceleration?
3. Inversely proportional or just proportional.....say if i get a question that says "a particle moves on a straight line with acceleration which is inversely proportional to t^3"....I would write a = k/t3? and if it was just proportional Id just write a = kt^3?
4. Not sure how this works........cos((pi.t)/180) = 0.75.....how this turns into t=(370/pi)inverse cos 0.75 = 85......not sure how the algebra works in it

any help is GREATLY appreciated!!
cheers

 

[alcalder]

hey guys, im having difficulty on some mechanics concepts
I dont do physics so please pardon my lack of knowledge....
1. How do you work out what the starting equation is? Like if its a straight line do you just write a=kv? and if slowing down a=-kv?

Depends of the conditions they give and proportionality etc. But, yes, slowing down means put a negative there.

2. Is retardation just negative acceleration?

YES

3. Inversely proportional or just proportional.....say if i get a question that says "a particle moves on a straight line with acceleration which is inversely proportional to t^3"....I would write a = k/t3? and if it was just proportional Id just write a = kt^3?

YES again, you;re doing well.

4. Not sure how this works........cos((pi.t)/180) = 0.75.....how this turns into t=(370/pi)inverse cos 0.75 = 85......not sure how the algebra works in it

Not quite sure how that works either. It should be

= (180/pi)inverse cos 0.75 = 41

What was the original context?

Hope that helped some.