Q. 194.6( 9 Votes )

# The force of buoyancy exerted by the atmosphere on a balloon is B in the upward direction and remains constant. The force of air resistance on the balloon acts opposite to the direction of velocity and is proportional to it. The balloon carries a mass M and is found to fall down near the earth’s surface with a constant velocity u. How much mass should be removed from the balloon so that it may rise with a constant velocity u?

Answer :

Given:

Buoyancy force = B

Velocity in both cases =

Air resistance is proportional to velocity

∴ resistive force = , where k is proportionality constant.

Case I:

When balloon is falling down with constant velocity,

Then equation for equilibrium becomes,

Case II:

When balloon is raising up with constant velocity after removing some mass,

Then equation for equilibrium becomes,

∴

∴ removed mass =

Rate this question :

Figure 5.9 shows (v_{x} ,t ),and( (v_{y} ,t) diagrams for a body of unit mass. Find the force as a function of time.

Physics - Exemplar

The door of an Amirah is 6 ft. high, 1.5 ft. wide and weighs 8 kg. The door is supported by two hinges situated at a distance of 1 ft. from the ends. If the magnitudes of the forces exerted by the hinges on the door are equal, find this magnitude.

HC Verma - Concepts of Physics Part 1Consider the following two equations

(A)

(B)

In non-inertial frames

HC Verma - Concepts of Physics Part 1