Home / Class 9 Science / Chapter 9 Force and Laws of Motion MCQ Test 2 Science Class 9 Science
Online Test of Chapter 9 Force and Laws of Motion 2 Science| Class 9th
1. According to Newton’s third law of motion, action and reaction
(i) always act on the same body
(ii) always act on different bodies in opposite direction
(iii) have same magnitudes and direction
(iv) act on either body at normal to each other
2. The minimum number of unequal forces that can make zero resultant is
(i) two
(ii) three
(iii) four
(iv) ten
3. An object of mass 2 kg is sliding with a constant velocity of 4 ms-1 on a frictional horizontal table. The force required to keep the object moving with same velocity is
(i) 2 N
(ii) 8 N
(iii) 32 N
(iv) 0 N
4. A mass M breaks into two pieces in the ratio 1 : 3 while at rest. If the heavier has a speed of v, the speed of the lighter is
(i) v
(ii) 2v
(iii) 3v
(iv) 4v
5. An object of mass of 2 kg is sliding with a velocity of 4 ms-1 on a frictional horizontal surface. The retarding force necessary to stop the object in 1 second is
(i) 2 N
(ii) 4 N
(iii) 8 N
(iv) 0 N
6. The two states of motion treated alike by the Newton’s first law, among A, B, C and D are
A : Rest
B : Uniform motion
C : Uniformly accelerated
D : Non-uniformly accelerated
(i) A, D
(ii) A, B
(iii) A, C
(iv) B, C
7. Passengers standing in a bus are thrown outwards when the bus takes a turn suddenly. This happens because of
(i) outward pull on them
(ii) inertia
(iii) change in momentum
(iv) change in acceleration
8. When a 12 N force acts on 3 kg mass for a second, the change in velocity is (in m/s)
(i) 36
(ii) 4
(iii) 2
(iv) 18
9. A force of ‘P* N acts on a particle so as to accelerate it from rest to a velocity ‘v’ m/s. The force ‘P’ is then replaced by ‘Q’ N which decelerates it to rest.
(i) P may be equal to Q
(ii) P must be equal to Q
(iii) P must be unequal to Q
(iv) none of these
10. Which of the following does not happen? As an automobile accelerates suddenly,
(i) a toy monkey hung from the roof moves back
(ii) a standing person gets pushed back
(iii) a bag at the roof gets displaced backward
(iv) a person in the seat is pushed in front
Class 9 Force and Laws Of Motion MCQ - 2
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Question 1 of 10
1. Question
According to Newton’s third law of motion, action and reaction
Correct
Incorrect
Question 2 of 10
2. Question
The minimum number of unequal forces that can make zero resultant is
Correct
Three vectors of unequal magnitude which can be represented by the three sides of a triangle taken in order, produce zero resultant.
Incorrect
Three vectors of unequal magnitude which can be represented by the three sides of a triangle taken in order, produce zero resultant.
Question 3 of 10
3. Question
An object of mass 2 kg is sliding with a constant velocity of 4 ms-1 on a frictional horizontal table. The force required to keep the object moving with same velocity is
Correct
According to Newton’s 1st Law: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Table is frictionless. No frictional force is acting on the body. Body is already in motion. It will be in motion with same uniform velocity unless an opposing force acts on it. So, no force (F = 0) is required for the body to keep it moving with same velocity.
Incorrect
According to Newton’s 1st Law: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Table is frictionless. No frictional force is acting on the body. Body is already in motion. It will be in motion with same uniform velocity unless an opposing force acts on it. So, no force (F = 0) is required for the body to keep it moving with same velocity.
Question 4 of 10
4. Question
A mass M breaks into two pieces in the ratio 1 : 3 while at rest. If the heavier has a speed of v, the speed of the lighter is
Correct
Incorrect
Question 5 of 10
5. Question
An object of mass of 2 kg is sliding with a velocity of 4 ms-1 on a frictional horizontal surface. The retarding force necessary to stop the object in 1 second is
Correct
Here, u = 0 m /s
a = v- u / t ⇒ 0-4/1 = -4
Formula of regarding force remains same.
F = – ma. ( negative sign comes due to restarting acceleration.)
Therefore, F = – 2* (-4)
F = 8 N
Incorrect
Here, u = 0 m /s
a = v- u / t ⇒ 0-4/1 = -4
Formula of regarding force remains same.
F = – ma. ( negative sign comes due to restarting acceleration.)
Therefore, F = – 2* (-4)
F = 8 N
Question 6 of 10
6. Question
The two states of motion treated alike by the Newton’s first law, among A, B, C and D are
A : Rest
B : Uniform motion
C : Uniformly accelerated
D : Non-uniformly accelerated
Correct
Incorrect
Question 7 of 10
7. Question
Passengers standing in a bus are thrown outwards when the bus takes a turn suddenly. This happens because of
Correct
Incorrect
Question 8 of 10
8. Question
When a 12 N force acts on 3 kg mass for a second, the change in velocity is (in m/s)
Correct
Incorrect
Question 9 of 10
9. Question
A force of ‘P* N acts on a particle so as to accelerate it from rest to a velocity ‘v’ m/s. The force ‘P’ is then replaced by ‘Q’ N which decelerates it to rest.
Correct
To decelerate a body, a force must be applied opposite to the direction of velocity, irrespective of its magnitude.
According to the condition of motion under two forces P and Q must be acting in opposite directions and may be equal, not necessarily must be equal.
Incorrect
To decelerate a body, a force must be applied opposite to the direction of velocity, irrespective of its magnitude.
According to the condition of motion under two forces P and Q must be acting in opposite directions and may be equal, not necessarily must be equal.
Question 10 of 10
10. Question
Which of the following does not happen? As an automobile accelerates suddenly,
Correct
When a vehicle accelerates and suddenly applies a break we possess what we call inertia. And when it suddenly applies a break we tend to retain that Velocity so we fall backwards thus satisfying the law of inertia or what is also called Newton’s first law of motion.
Incorrect
When a vehicle accelerates and suddenly applies a break we possess what we call inertia. And when it suddenly applies a break we tend to retain that Velocity so we fall backwards thus satisfying the law of inertia or what is also called Newton’s first law of motion.
