Tamil Nadu Board Class 7 Science Chapter 2 Force and Motion
if you are looking for Tamil Nadu Board Class 7 Science Chapter 2 Force and Motion then you are at the right place. Here we are providing solutions as well as additional QA / Important Notes.
Choose the best answer.
A particle is moving in a circular path of radius r. The displacement after half a circle would be…….
- Zero
- R
- 2r
- r/2
Suppose a boy is enjoying a ride on a merry go round which is moving with a constant speed of 10 m/s. It implies that the boy is …
- at rest
- moving with no acceleration
- in accelerated motion
- moving with uniform velocity
How can we increase the stability of an object?
- Lowering the centre of gravity
- Raising the centre of gravity
- Increasing the height of the object
- Shortening the base of the object
Fill in the blanks.
- The shortest distance between two places is………[straight line]
- The rate of change of velocity is…….[accelaration]
- If the velocity of an object increases with respect to time, then the object is said to be in …….. acceleration.[positive]
- The slope of the speed-time graph gives……………..[accelaration]
- In ………..equilibrium, the centre of gravity remains at the same height when it is displaced.[neutral]
Match the Following:
Displacement – Metre
Light travelling through vacuum – Uniform velocity
Speed of ship – Knot
Centre of gravity of geometrical shaped objects – Geometric centre
Stability – Larger base area
Analogy
- Velocity: metre/second :: Acceleration: metre/second²
- Length of scale: metre :: Speed of aeroplane : knot
- Displacement / Time: Velocity: Speed/ Time: Speed
Â
Answer briefly
Q- Asher says all objects having uniform speed need not have uniform velocity. Give reason.
An object can have a uniform speed while still changing its direction. For instance, a car moving at a constant speed around a circular track has uniform speed, but its direction is continuously changing, so its velocity is not uniform. Velocity includes both speed and direction. Thus, uniform speed does not guarantee uniform velocity because velocity depends on the consistency of both magnitude and direction.
Q- Â Saphira moves at a constant speed in the same direction. Rephrase the same sentence in fewer words using concepts related to motion.
Saphira moves with uniform velocity.
Q- Â Correct your friend who says that acceleration gives the idea of how fast the position changes.
Acceleration does not describe how fast the position changes; it describes how fast the velocity changes. Velocity is the rate of change of position, while acceleration is the rate of change of velocity. Thus, acceleration indicates changes in speed or direction over time, not position directly.
Answer these
Q- Distinguish between speed and velocity.
Speed is a scalar quantity that refers to how fast an object is moving. It is the rate at which an object covers distance and does not consider direction. Speed is calculated as distance divided by time (speed = distance/time) and is measured in units like meters per second (m/s).
Velocity is a vector quantity that refers to the rate at which an object changes its position. It includes both the speed of the object and the direction of its motion. Velocity is calculated as displacement divided by time (velocity = displacement/time) and is also measured in meters per second (m/s). Therefore, velocity can change even if the speed is constant if the direction changes.
Q- What do you mean by constant acceleration?
Constant acceleration means that the rate of change of velocity of an object is the same over time. This implies that the object’s velocity is increasing or decreasing by a consistent amount each second. An example of constant acceleration is free fall under gravity, where an object accelerates downwards at approximately 9.8 m/s². In mathematical terms, if acceleration a is constant, then the velocity v at time t is given by v=u+at, where u is the initial velocity.
Q- What is centre of gravity?
The center of gravity of an object is the point through which the entire weight of the object appears to act. It is the average location of the weight distribution of the object. For symmetrical and uniform objects, the center of gravity typically lies at the geometric center. However, for irregularly shaped objects, the center of gravity might be closer to one side. The center of gravity is crucial in determining the stability of objects; a lower center of gravity generally implies greater stability.
Numerical Problems:-
Q- Geetha takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.
   Given:
