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An ornament weighing 36 g in air, weighs only 34 g in water. Assuming that some copper is mixed with gold to prepare the ornament, find the amount of copper in it. Specific gravity of gold is 19.3 and that of copper is 8.9.
Concept: undefined >> undefined
Refer to the previous problem. Suppose, the goldsmith argues that he has not mixed copper or any other material with gold, rather some cavities might have been left inside the ornament. Calculate the volume of the cavities left that will allow the weights given in that problem.
Concept: undefined >> undefined
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A cylindrical object of outer diameter 20 cm and mass 2 kg floats in water with its axis vertical. If it is slightly depressed and then released, find the time period of the resulting simple harmonic motion of the object.
Concept: undefined >> undefined
A cylindrical object of outer diameter 10 cm, height 20 cm and density 8000 kg/m3 is supported by a vertical spring and is half dipped in water as shown in figure. (a) Find the elongation of the spring in equilibrium condition. (b) If the object is slightly depressed and released, find the time period of resulting oscillations of the object. The spring constant = 500 N/m.
Concept: undefined >> undefined
A cube of ice of edge 4 cm is placed in an empty cylindrical glass of inner diameter 6 cm. Assume that the ice melts uniformly from each side so that it always retains its cubical shape. Remembering that ice is lighter than water, find the length of the edge of the ice cube at the instant it just leaves contact with the bottom of the glass.
Concept: undefined >> undefined
A wooden block with a coin placed on its top, floats in water as shown in figure. The distance l and h are shown in the figure. After some time the coin falls into the water. Then ______.
- l decreases.
- h decreases.
- l increases.
- h increase.
Concept: undefined >> undefined
Read the statement below carefully and state, with reason and example, if it is true or false:
A particle in one-dimensional motion with constant speed must have zero acceleration.
Concept: undefined >> undefined
Read the statement below carefully and state, with reason and example, if it is true or false:
A particle in one-dimensional motion with positive value of acceleration must be speeding up.
Concept: undefined >> undefined
Suggest a suitable physical situation for the following graph:
Concept: undefined >> undefined
The given figure gives a speed-time graph of a particle in motion along a constant direction. Three equal intervals of time are shown. In which interval is the average acceleration greatest in magnitude? In which interval is the average speed greatest? Choosing the positive direction as the constant direction of motion, give the signs of v and a in the three intervals. What are the accelerations at the points A, B, C and D?
Concept: undefined >> undefined
On a long horizontally moving belt (Fig. 3.26), a child runs to and fro with a speed 9 km h–1 (with respect to the belt) between his father and mother located 50 m apart on the moving belt. The belt moves with a speed of 4 km h–1. For an observer on a stationary platform outside, what is the
(a) speed of the child running in the direction of motion of the belt ?.
(b) speed of the child running opposite to the direction of motion of the belt ?
(c) time taken by the child in (a) and (b) ?
Which of the answers alter if motion is viewed by one of the parents?
Concept: undefined >> undefined
If a particle is accelerating, it is either speeding up or speeding down. Do you agree with this statement?
Concept: undefined >> undefined
Give example where the velocity of a particle is zero but its acceleration is not zero.
Concept: undefined >> undefined
Give example where the velocity is opposite in direction to the acceleration.
Concept: undefined >> undefined
Give example where the velocity is perpendicular to the acceleration.
Concept: undefined >> undefined
In figure shows the x coordinate of a particle as a function of time. Find the sings of vx and ax at t = t1, t = t2 and t = t3.
Concept: undefined >> undefined
A stone is released from an elevator going up with an acceleration a. The acceleration of the stone after the release is
Concept: undefined >> undefined
The accelerations of a particle as seen from two frames S1 and S2 have equal magnitude 4 m/s2.
Concept: undefined >> undefined
An object having a velocity 4.0 m/s is accelerated at the rate of 1.2 m/s2 for 5.0 s. Find the distance travelled during the period of acceleration.
Concept: undefined >> undefined
What can be said about the centre of mass of a uniform hemisphere without making any calculation? Will its distance from the centre be more than r/2 or less than r/2?
Concept: undefined >> undefined
