For idea gases, volume is directly proportional to temperature. That is, an increase in temperature leads to increase in volume and vice versa.
Therefore,
V1/T1 = V2/T2 => T2 = (V2*T1)/V1
Assuming that the balloon is spherical in shape,
V= 4/3*pi*R^3.... In the formula for calculating T2, 4/3*pi cancels out.
R1 = 30/2 15 cm; R2 = 30.5/2 = 15.25 cm; T1 = 20+273.15 =293.15 K
Therefore,
T2 = (R2^3*T1)/R1^3 = (15.25^3*293.15)/15^3 = 308.05 K = 34.9 °C
Answer:C
Explanation:
When a constant horizontal force is applied to the box, box started moving in the horizontal direction such that it moves with constant velocity 
Constant velocity implies that net force on the box is zero
i.e. there must be an opposing force which is equal to the applied force and friction force can serve that purpose.
So option c is the correct choice.
Take into account that density and relative density are given by:

Take into account that the volume associated to each of the given sustances in the table is determined by the Level Difference (because it is the change in the volume of the water of the recipient in which the substance is immersed).
The density of water in kg/m^3 is 1000 kg/m^3.
Due to the density must be given in kg/m^3, it is necessary to express the volumes of the table in m^3 and mass in kg, then, consider the following conversion factor:
1 m^3 = 1000000 ml
1 kg = 1000 g
Then, you obtain the following results:
Brass:

Cooper: