Motion and Measurement of Distances Test - 3

When an object moves along a circular path, it is called circular motion. During such a motion, the direction of motion at any point is given by the tangent at that point which changes continuously.

Displacement of the cyclist = Shortest distance between P and Q  

When a body moves from one position to another, the shortest distance measured between the initial and the final positions of the moving body in a particular direction is called displacement. The actual length of the path travelled by a moving body in a given interval of time is called the distance travelled by that body. So displacement of a body may be zero, though distance can be finite. For example, in case of circular motion if the body comes back to its initial position then distance travelled is finite but displacement is zero.

The property of a body by virtue of which it resists any change in its state of rest or of motion in a straight line on its own is called its inertia.

A rider on horse falls back when horse starts running, all of a sudden because the rider is in state of rest initially and later inertia of rest keeps the upper part of body at rest while lower part of the body moves forward with horse.

As 20 divisions = 1 cm ∴    1 division = 1/20 cm= 0.05 cm =0.5 mm Hence, least count of this scale = 0.5 mm

Only (ii) shows the periodic as well as oscillatory motion. It is showing to and fro as well as motion which is repeating after regular time interval.

Motion of soldiers on march past is rectilinear motion; Every oscillatory motion is also a periodic motion; Hockey player running after a ball is random motion.

P = 2.1 cm; Q = 3.0 cm; R = 3.1 cm; S = 2.5 cm Average length of these sticks =P+Q+R+S/4= 2.6 cm

Rahul takes path XOY and Ravi takes path XY. Displacement is minimum distance between initial and final point = XY.

Rahul and Ravi both cover different distances XOY and XY respectively at the same time. Rahul covers more distance than Ravi in the same time. Hence Rahul covers longer distance with a higher speed.

The length of the wooden box = Difference between the reading at both the ends

=4.7−1.5=3.2 cm 

Motion of strings of a guitar shows oscillatory as well as vibratory motion.

In case of collision, changes are most likely to be appear in the speed and direction of both the balls.

The time taken to complete one oscillation is called the time period of a pendulum.   Here the time period is the time taken to move from Y to B then back to A and then to Y. The reading of stopwatch = T Number of oscillations = 10 ∴ Time taken =Time period/Number of oscillations                                     =T/10

Initial volume of water in the cylinder, (before the immersion of the object) V1= 70cm³ Final volume in the cylinder (after the immersion of the object) V2= 82cm³ Hence, volume of the object immersed in the cylinder = Final volume - Initial volume = 82 cm³ −70 cm³ =12 cm³

Length of the thread placed on scale= 13.5 cm As thread is folded 6 times, ∴ Length of the thread =13.5×6 cm= 81 cm= 0.81 m

Measurement is the comparison of an unknown quantity with a known quantity.

Metre is a standard unit of measurement

The S.I. unit of length is metre.

Positions P and Q do not give accurate readings on the ruler because they cause parallax error.

1m=1000 mm Hence, thousandth fraction of 1 metre is 1 mm

1 km= 1000 m= 10⁶ mm Hence, the ascending order of magnitudes of length is mm, m, km.

The choice of a length-measuring device depends upon the type of measurement to be made. For example, a thin wire, the length of a pencil, distance between two stars etc., are to be measured, then the type of measurement changes. A thin hair strand cannot be measured by using a ruler. To measure it, a screw gauge is used.

According to the figure, the length of the given object  =5−1.8=3.2 units.

The length of a curved surface is measured by using both the metre scale and the thread.

A measuring tape is used by tailors, for taking body measurements