Here are a few questions. I urgently need help. Thanksssss!
1. Usually, we are told that at the maximum displacement, when v
= 0 ms-1, the acceleration is only that of gravity, 9.81 ms-2. May
I know if this case only applies in circumstances when air
resistance is negligible? If yes, what happens if A.R must be taken
into account, acc. is lower?
2.A ball is thrown with a velocity of 26 ms-2 vertically upwards
and has 0ms-1 at 1.8s.
Just after the ball leaves the thrower's hands, it has a
downward acceleration of approximately 20ms-1. Explain how this is
possible.
My explanation is rather brief, it circles around the fact that
the downward forces Wball and Fd (drag force) > g so
acceleration will have value greater than 9.81 ms-2. Do I have to
make calculations to show that the downward acceleration is around
20ms-2?
3.When you have acceleration-time graph in the -ve region and
moving downwards (which originates from a point in the +ve region),
how do you know that velocity is in +ve or -ve region? Because -ve
acceleration doesn't mean -ve velocty. I always have probs trying
to translate v-t and s-t graphs given a-t graphs, especially when
the a-t graphs are curves... any helpful sources to help me
understand better? I need a lot of representations to
understand.
4.
X
O___________________P________________Q
*X in the above diagram represents max height reached by ball x,
which is directly above P
Ball X of mass m is projected with a speed of u from O at an
angle alfa (let's give it a symbol 'a') above the horizontal and it
raeches its max. height directly above point P.
Ball Y of mass 2m is projected towards P with speed of 2u from O
also at an agle of 'a' above the horizontal. Deduce Y's horizontal
displacement when it reaches it s max.height. (Q is twice as far
away from O as P)
Not sure how throwing another ball of double the mass and spped
will have implications on the horizontal displacement... I suppose
this is a projectile question but I really dont see how knowing
ball Y has double the mass of ball X enables me to solve this
question. Do help me in solving this question.