What is the velocity of a rubber ball dropped from a rooftop after 3 seconds?

A. 0.31 m/s
B. 3.27 m/s
C. 6.8 m/s
D. 29.4 m/s

Assume that the acceleration downwards = gravitational field strength = 9.8 (2 s.f)

Assume that the mass of the ball is negligible and there is no air resistance.

Use the equation  =+1/22

s

=

u

t

+

1

/

2

a

t

2

s=height of building

t= time taken for the ball to drop

u=initial velocity ; this = 0, because when the ball is dropped it has no speed initially, however if the question had said projected instead of dropped then it must have an initial speed. In this scenario we assume it has 0 initial speed since the question says dropped.

Substitute values to equation :

s=(0*3)+(1/2*9.8*3^2)

s=(1/2*9.8*3^2)

s=44.1m

Explanation:

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂