Last Updated on December 24, 2024 by XAM CONTENT
Hello students, here you will find numerical on force and laws of Motion with answers. Before we start solving the numerical, let’s see some important points and formulae. This will help you to solve the problems efficiently.
| Topic | Force and Laws of Motion |
| Type of Questions | Numerical Problems |
| Nature of Questions | Formula Based |
| Board | CBSE |
| Class | 9 |
| Subject | Science – Physics |
| Useful for | Class 9 Studying Students |
| Answers provided | Yes |
| Difficulty level | Mentioned |
| FAQ | Provided |
| Important Link | Class 9 Physics Topicwise Numerical Problems |
Understanding Force and Laws of Motion
Force and the laws of motion are fundamental concepts in physics that help us understand how objects move and interact. Here’s a brief explanation to lay the foundation for solving numerical problems:
What is Force?
Force is a push or pull that acts on an object due to its interaction with another object. It can change the object’s state of motion, direction, or shape. Force is a vector quantity, meaning it has both magnitude and direction, and is measured in newtons (N). The formula for force is:
$$
F=m a
$$
Where:
– $F$ is the force (in newtons),
– $m$ is the mass of the object (in kilograms),
– $a$ is the acceleration (in meters per second squared).
Newton’s Laws of Motion
- First Law (Law of Inertia): An object will remain at rest or continue to move in a straight line at constant velocity unless acted upon by an external force. This explains why objects resist changes to their motion.
- Second Law: The force acting on an object is directly proportional to the product of its mass and acceleration. This law forms the basis for solving numerical problems and is mathematically expressed as: F=ma
- Third Law: For every action, there is an equal and opposite reaction. This means forces always occur in pairs, acting on different objects.
The rate of change of momentum of a body is proportional to the applied force and this change in momentum occurs in the direction of the applied force.
In the below section, we are providing numerical problems on Force and Laws of Motion for Class 9 Physics.
Numerical Problems on Force and Laws of Motion with Answers
Formula used:
Units used:
SI unit of force is newton (N).
SI unit of momentum is kg.m/s
Numerical Problem 1:
The mass of a cannon is 500 kg and it recoils with a speed of 0.25 m/s. What is the momentum of the cannon?
Difficulty Level: Easy
Check Answer
Momentum
= m × v
= 500 × 0.25
= 125 kg·m/s
Numerical Problem 2:
2 balls have masses of 50 gm and 100 gm and they are moving along the same line in the same direction with velocities of 3 m/s and 1.5 m/s respectively. They collide with each other and after the collision, the first ball moves with a velocity of 2.5 m/s. Calculate the velocity of the other ball after collision.
Difficulty Level: Medium
Check Answer
Solution:
\( m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2 \)
\( (0.05 \times 3) + (0.1 \times 1.5) = (0.05 \times 2.5) + (0.1 \times v_2) \)
\( \frac{150}{1000} + \frac{150}{1000} = \frac{125}{1000} + \frac{100 v_2}{1000} \)
\( \frac{300}{1000} = \frac{125 + 100 v_2}{1000} \)
\( 300 = 125 + 100 v_2 \)
\( 100 v_2 = 175 \)
\( v_2 = \frac{175}{100} \)
\( v_2 = 1.75 \, \mathrm{m/s} \)
Numerical Problem 3:
An object of mass 16 kg is moving with an acceleration of 3 m/s2. Calculate the applied force. If the same force is applied on an object of mass 24 kg, how much will be the acceleration?
Difficulty Level: Medium
Check Answer
Solution:
\( F_1 = m_1 \times a_1 \)
\( F_1 = 16 \times 3 \)
\( F_1 = 48 \, \mathrm{N} \)
\( F_2 = m_2 \times a_2 \)
\( a_2 = \frac{F_2}{m_2} \)
\( a_2 = \frac{48}{24} \)
\( a_2 = 2 \, \mathrm{m/s}^2 \)
Numerical Problem 4:
A bullet has a muzzle velocity of 300 m/s. The gun of mass 3 kg has a recoil velocity of ‘v’. Calculate ‘v’. Mass of the bullet is 30 grams.
Difficulty Level: Medium
Check Answer
Ans. 3 m/sNumerical Problem 5:
A force of 10 N acts on a body of mass 2 kg for 3 s, initially at rest. Calculate: (i)Velocity acquired by the body. (ii) Change in momentum of the body.
Difficulty Level: Medium
Check Answer
Ans. (i) 15 m/s (ii) 30 kg m/sNumerical Problem 6:
If the momentum of a body of mass 10 kg is 20 kg m/s, find its velocity.
Difficulty Level: Easy
Check Answer
Ans. 2 m/sNumerical Problem 7:
A body of mass 5 kg moves with an acceleration of 4 m/s2. Calculate its change in momentum in 3 seconds.
Difficulty Level: Medium
Check Answer
Ans. 60 kg m/sNumerical Problem 8:
A body of mass 5 kg moves with an acceleration of 2 m/s2. Find the change in momentum of the body in 2 seconds.
Difficulty Level: Medium
Check Answer
Ans. 20 kg m/sHelpful Links for CBSE Class 9 Science Preparation
- Download Latest Sample Papers for CBSE Class 9 Science
- Download Worksheets for CBSE Class 9 Science
- Download Chapter Tests for CBSE Class 9 Science
- Download Case Study Question Bank for CBSE Class 9 Science
- Download Numerical Problems for CBSE Class 9 Physics
- Download Important MCQs for CBSE Class 9 Physics
Frequently Asked Questions (FAQs) on Force and Laws of Motion Numerical Problems
Q1: What is force?
A1: Force is a push or pull acting on an object as a result of its interaction with another object. It can change the object’s state of motion, direction, or shape. Force is measured in newtons (N) and is a vector quantity, meaning it has both magnitude and direction.
Q2: How do numerical problems prepare students for exams?
A2: Numerical problems prepare students for exams in several ways:
Practice and Familiarity: Regular practice with numerical problems makes students familiar with the types of questions they may encounter in exams.
Time Management: Solving numerical problems helps students develop the ability to manage their time effectively during exams.
Confidence Building: Successfully solving numerical problems boosts confidence, reducing exam anxiety.
Error Identification: It helps students identify common mistakes and learn from them, improving accuracy in exams.
Q3: Why are numerical problems useful for understanding physics?
A3: Numerical problems are useful for understanding physics because:
Practical Application: They allow students to apply theoretical knowledge to practical situations, enhancing understanding.
Critical Thinking: They encourage critical thinking and logical reasoning, essential for comprehending physical phenomena.
Interconnected Concepts: They demonstrate how different concepts in physics are interconnected, providing a holistic understanding.
Visualization: They often involve diagrams and visual aids, helping students visualize and grasp abstract concepts better.
Q4: What are the key steps to solve numerical problems on force and laws of motion?
A4: The key steps to solve numerical problems on force and laws of motion are:
Read the Problem Carefully: Understand the given data and what is being asked.
Identify the Known and Unknown Variables: List out the known quantities and what needs to be calculated.
Select the Appropriate Formula: Choose the correct formula based on the known and unknown variables.
Perform the Calculations: Substitute the known values into the formula and solve for the unknown.
Check the Units: Ensure the units are consistent and convert them if necessary.
Review the Answer: Check if the answer is reasonable and verify it with the context of the problem.
Q5: What tips can help students improve their skills in solving numerical problems?
A5: Here are some tips to improve skills in solving numerical problems:
Practice Regularly: Consistent practice is key to mastering numerical problems.
Understand the Concepts: Ensure a strong grasp of the underlying concepts before attempting problems.
Review Mistakes: Learn from errors by reviewing and understanding where you went wrong.
Q6: Are there any online resources for practicing numerical problems on force and laws of motion?
A6: Yes, there are several online resources available for practicing numerical problems, including:
Educational Websites: Websites like Physics Gurukul offer practice problems and tutorials.
xamcontent.com: Xam Content also offers numerical problems on different topics for all classes.
Q7: What is momentum?
A7: Momentum is the product of an object’s mass and its velocity. It is a vector quantity and is given by, p = mv. The SI unit of momentum is kg·m/s.
Q8: What is the SI unit of force?
A8: The SI unit of force is the newton (N). One newton is the force required to accelerate a 1 kg mass by 1 m/s².
