Showing posts with label Chapter 3: FORCES AND MOTION. Show all posts
Showing posts with label Chapter 3: FORCES AND MOTION. Show all posts

Friday, May 5, 2023

CHAPTER 3 FORCES AND MOTION

 

3.1      Choose the best option.

1.Figure given below shows the motion of the body. Calculate its displacement.



 








(a) 6 m

(b) 7 m

(c) 8 m

(d) 23 m

2.      Acceleration due to uniform velocity of a body is:

(a) Positive

(b) Negative

(c) Maximum

(d) Zero

3.      Third equation of motion is independent of:

(a) Time

(b) Displacement

(c) Velocity

(d) Acceleration

4.     


 

 
What is the speed of the cyclist between two points S1 and S2 as shown in figure.

(a) 10 km h-1

(b) 20 km h-1

(c) 30 km h-1

(d) 50 km h-1


5.      What will be the velocity of a body when it starts its motion from rest and after 5s its acceleration becomes 2 ms-2

(a) 5 ms-1

(b) 10 ms-1

(c) 25 ms-1

(d) 50 ms-1

6.      What is the velocity of an object when it reaches from point P to point Q in 2s along a semicircle of radius 2m?

 

(a) zero

(b) 1 ms-1

(c) 2 ms-1

(d) 4 ms-1

7.      The S.I unit of weight is;

(a) Gram

(b) kilogram

(c) Pound

(d) Newton

8.      What is the acceleration produced by a force of 0.5 N applied on a body of mass 0.1 kg?

(a) 0.1 ms-2

(b) 0.5 ms-2

(c) 1 ms-2

(d) 5 ms-2



9.      Three masses which are connected by a mass less spring as shown in figure. What will be the value of force F2?

 

(a) 15 N

(b) 18 N

(c) 24 N

(d) 30 N

10.      Rate of change of momentum is

(a) Impulse

(b) Force

(c) Torque

(d) Velocity

11.      A body moves from point P to point Q with a speed of 6 ms-1 along a straight Line then from Q to P with a speed of 4 ms-1. What is its average speed over the entire trip?

(a) 4 ms-1

(b) 4.8 ms-1

(c) 5 ms-1

(d) 5.5 ms-1

12.      What is the value of impulse in the force-time curve as shown in figure. 

(a) 1200 N-s

(b) 1350 N-s

(c) 1500 N-s

(d) 1650 N-s

13.      Impulse has always changed.

(a) Energy

(b) Momentum

(c) Velocity

(d) Acceleration

14.      In one-dimension elastic collision of two bodies of same masses, what will Happen? When a moving body is colliding with the rest one;

(a) Their velocities will be interchanged

(b) Velocities of both bodies will be zero

(c) Moving body will continue its motion

(d) Moving body will come at rest and the rest one will start its motion

15.      In projectile motion, the horizontal component of acceleration of a body is;

(a) Zero

(b) Accelerated

(c) Decelerated

(d) Maximum

16.      At what angle a projectile body gains its maximum height

(a) 0°

(b) 45°

(c) 60°

(d) 90°

17.      A rocket is working on basis of

(a) Newton’s First law

(b) Newton’s 2nd law

(c) Newton’s 3rd law

(d) All of these

18.      The vertical and horizontal distances will be equal if angle of projection is:

(a) 45°

(b) 56°

(c) 66°

(d) 76°

19.      The quantitative measure of inertia of a body is its:

(a) Mass

(b) Weight

(c) Velocity

(d) Momentum

Answers

  1. (b) 7 m
  2. (d) Zero
  3. (a) Time
  4. (c) 30 km h-1
  5. (b) 10 ms-1
  6. (c) 2 ms-1
  7. (d) Newton
  8. (d) 5 ms-2
  9. (c) 24 N
  10. (b) Force
  11. (c) 5 ms-1
  12. (b) 1350 N-s
  13. (b) Momentum
  14. (d) Moving body will come at rest and the rest one will start its motion
  15. (a) Zero
  16. (d) 90°
  17. (d) All of these
  18. (d) 76°
  19. (a) Mass

3.2      Short question

 1.      When the magnitude of distance and displacement are equal?

ans.  When the motion is in a fixed direction.

      2.      Is it necessary, when the acceleration of a body is zero then its velocity is also zero?

ans. No, it's not necessary for the velocity of a body to be zero when its acceleration is zero. If a body is moving at a constant velocity, its acceleration is zero even though it has a non-zero velocity. For example, if you throw a ball straight up into the air, at the highest point of its trajectory it is zero velocity but having a non-zero acceleration.

  16.      If you kick a stone in 1/100 seconds and 1/10 seconds time intervals. In which Condition you hurt most?

ans.    Kicking a stone in 1/100 seconds will hurt your foot more than kicking it in 1/10 seconds because of the higher impact force.

19. At what projected angle the horizontal range and maximum height are equal?


21. How has the speed of a rocket increased?

ans.    By increasing the acceleration of the rocket which can be achieved by decreasing the mass of the rocket


Rocket burns the fuel which decrease the net mass (Δm), increasing the acceleration and rocket get up thrust.

3.3      Numerical problems

1.      A train moves with a uniform velocity of 24 ms-1. The driver applies the Brakes, and the train comes to rest with a uniform retardation in 12 s. Find (i) The retardation, (ii) velocity of the train after 4 sec and (ii) distance travels by train after the brakes are applied.



6.      What is the recoil velocity of 6 kg gun if its shoots a 9 g bullet out of the muzzle at velocity of 350 ms-1.


9.      A cricket ball is hit upward at an angle 45° with velocity of 20 ms-1, find (a) The maximum height (b) time of flight (c) How far away it hits the ground.