kinematics q. (1 Viewer)

[skillz]

A particle travels in a straight line with a constant velocity of 4m/s for 12 seconds. It is then subjected to a constant acceleration in the opposite direction for 20 seconds which returns the particle to its original position. find

a) the acceleration of the particle.






cheers

 

[skillz]

Thanks dude.

new q.

The maximum rate at which a bus can accelerate or decelerat is 2/ms^2, it has a maximum speed of 60km/h. Find the shortest time the bus can take to travel betwen two bus stops 1km apart on a straight stretch of road.

my workings out is..

maximum velocity is 60km/h or 50/3 m/s.
it takes 25/3 seconds to accelerate to 60 km/hr therefore 50/3 seconds to accelerate/decelerate in total which covers 278 metres?.
it is constant for 722m and it will take 43.32 seconds at 50/3 m/s to cover that.
which adds up to around 60 seconds.

but the answers different.

 

[Riviet]

Are you allowed to use the equation v²=2ax without deriving it? Because if you are, it is much quicker in situations like this (when you don't have to find out the time directly).

I believe we aren't allowed to use any physics formulae or any formulae at all other than the simple ones like speed=distance/time. So any standard forms of equations should to be derived, particularly in projectiles and motion questions.