Download physics class 9 chapter 2 conceptual questions federal board, national book foundation. These notes are also very helpful for kpk and federal board students. To find these notes you can search fazal academy physics notes pdf, fazal academy physics notes pdf class 9, fbise physics class 9 notes, federal board physics class 9 notes.
Unit 2: Kinematics
Exercise Conceptual Questions
Q1: In a park, children are enjoying a ride on big wheel as shown. What kind of motion the big wheel has and what kind of motion the riders have?
Ans: Motion of big wheel is rotatory Motion: Big wheel is rotating about its axis, so the motion of the wheel is rotatory motion.
Motion of riders is circular motion: Children are not rotating, they are moving in a circular path, so the motion of the children is circular motion.
Q2: A boy moves for some time, gives two situations in which his displacement is zero but covered distance is not zero?
Ans: If starting and ending points are same then displacement will be zero but covered distance is not zero.
Case 1: When a boy moves on a straight line from A to B and comes back from B to A then his displacement is zero because starting and ending points are same but covered distance is not zero which is equal to 5+5 = 10 (if 5 ⇄ 5 ).
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Q3: A stone tied to string is whirling in circle, what is direction of its velocity at any instant?
Ans: When a stone moves in a circle then the direction of its velocity is always tangent to the circle which is perpendicular to the direction of centripetal force or radius of circle.
Q4: Is it possible to accelerate an object without speeding it up or slowing it down?
Ans: Yes, it is possible.
Example: When an object moves in a circular path, the object has acceleration due to change in direction.
In this case, the object moves with constant speed i.e its speed neither increases nor decreases.
Q5: Can a car moving towards right have direction of acceleration towards left?
Ans: Yes
If a car is moving towards right then direction of velocity and acceleration is same i.e towards right.
When we apply brakes on the car then its speed decrease and deceleration is produced in it. In this case the direction of velocity is towards right but the direction of acceleration is towards left.
Q6: With the help of daily life examples, tell the situation in which
- Acceleration is in the direction of motion,
- Acceleration is against the direction of motion,
- Acceleration is zero and body is in motion.
Ans:
- If a car is moving in a straight line with increasing speed then the acceleration is in the direction of motion.
- When we apply brakes on the car then its speed decrease and deceleration is produced in it. In this case the acceleration is against the direction of motion.
- If the car is moving with uniform speed then its velocity does not change with time. So in this case acceleration is zero but the car is in motion.
Q7: Question 7 is available in pdf given below.
Q8: Which controls in the car can produce acceleration or deceleration in it ?
Ans:
- Accelerator: Acceletor in the car increases the speed of the car when pressed, so it produces acceleration in the car.
- Brakes: Brakes in the car decrease the speed of the car when pressed, so brakes produce deceleration in the car.
Q9: If two stones of 10kg and 1kg are dropped from a 1km high tower. Which will hit the ground with greater velocity? Which will hit the ground first? (neglect the air resistance)
Ans:
If two stone of 10kg and 1kg dropped from a 1km high tower then the heavier stone will hit the ground with greater velocity. Beacause the force with which Earth attract the body towards its centre is equal to the weight of the object. So the stone having mass 10kg will hit the ground with greater velocity.
If we neglect air resistance then both the stones will reach on the ground at same time.
Q10: A 1kg steel ball is dropped (from rest) and another is thrown downward with velocity of 5ms^-1 , which will have greater acceleration? (neglect the air resistance).
Ans: There are two steel balls each of which is 1kg. One is dropped (from rest) and other is thrown downward with 5ms^-1. Both of these ball are moving under the force of gravity with an acceleration g=10ms^-2. So both of balls will have same acceleration independent of their masses.
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