7th-Physics-TN(state board)-chapter8-Heat

 TN(state board)-chapter-Heat

1. International unit of measuring temperature is ..........................

        

          a. Kelvin                          b. Fahrenheit

          c. Celsius                         d. Joule

2. In thermometer when bulb comes in contact with hot object, liquid inside it

          a. expands                        b. contracts

          c. remains same               d. none of above

3. The body temperature of a healthy man is;

            a. 0°C    b. 37°C   c. 98°C      d. 100°C

4. Mercury is often used in laboratory thermometers because it

_______________________

            a. is a harmless liquid

            b. is silvery in colour and is attractive in appearance

            c. Expands uniformly

            d. is a low cost liquid

5. Which of the following temperature conversions is incorrect

       K ( Kelvin) = °C ( Celsius) + 273.15

       °C                                          K

a.-273.15                                  0

     b.  -123.                                  +150.15

     c.  + 127.                                + 400.15

     d.  + 450                                 + 733.15

              7th-TN(state board)-chapter-Force and Motion

Choose the best answer.

1. A particle is moving in a circular path of radius r. The displacement after half a circle would be

a. Zero

 b. R

c. 2 r

d. r / 2

Explanation: Ans: c

Displacement at half path is the shortest distance between the initial and final point. So, it's equal to twice the radius of the circle =2r.

2. From the given v-t graph it can be inferred that the object is

a. in uniform motion

b. at rest

c. in non uniform motion

d. moving with uniform acceleration

Explanation: Ans: d

An object undergoes uniform acceleration when the change (increase or decrease) in its velocity for every unit of time is the same.

3. Which of the following figures represent uniform motion of a moving object correctly?

Explanation: Ans: d

4. Suppose a boy is enjoying a ride on a marry go round which is moving with a constant speed of 10 m/s. It implies that the boy is

a . at rest

b.  moving with no acceleration

    c.  in accelerated motion

         d.  moving with uniform velocity

Explanation: Ans: c

Acceleration is the measure of how fast the velocity changes. Velocity is a vector quantity and a change in velocity is due to change in magnitude or change in direction or both.  Here, the boy is moving with constant speed but velocity changes and hence is supposed to be in accelerated motion.

5. What is one way you might increase the stability of an object?

a. lower the centre of gravity

b. raise the centre of gravity

c. increase the height of the object

d. shorten the base of the object

Explanation: Ans: a

The position of the centre of gravity of an object affects its stability. The lower the centre of gravity is, the more stable the object. The higher it is the more likely the object is to topple over if it is pushed. In general, increasing the size of the base (that is area) of support increases stability.