Question

A rubber ball is dropped from a height of 5m on a plane.On bouncing it rises to
1.8m . The ball loses its velocity by a factor of

A)3/5 B)2/5 C)16/25 D)9/25

Answer 1

@adeebabbas

We first need to calculate the final velocity of the the rubber ball. Then we need to calculate to find the initial velocity while it bounces back.@adeebabbas

We first need to calculate the final velocity of the the rubber ball. Then we need to calculate to find the initial velocity while it bounces back.

Answer 2

Use the equation \(\sf v^2=u^2+2as\)

For the first part,
initial velocity(u)=0
s=5
a=10
find v

For second part,
v=0
a=-10
s=1.8
Calculate u

Finally compare the two quantities you calculated in the above two parts.

Answer 3

no a is always -10. the acc. vector never changes.

Answer 4

@saeeddiscover

sign of acceleration or any vector depends upon the frame of reference.

Answer 5

When the motion in the direction of acceleration, the sign of acceleration is positive but when the motion is in opposite direction of acceleration then you take its value negative (because it's retardation in that case).

Answer 6

you are absolutely wrong. the frame of reference is chosen to be directed upward positive. the acceleration vector is ALWAYS pointed toward the earth, i.e it is always negative if we choose the y-positive to be upward. It does not depend on the direction of motion.