Newton's First Law Practice Problems And Answers Pdf
Newton's first law of motion is one of the most fundamental concepts in physics. It is also known as the law of inertia. This law states that an object at rest will remain at rest, and an object in motion will continue in motion with a constant velocity, unless acted upon by an external force.
This law has various applications in our daily lives, from the motion of vehicles on roads to the behavior of planets in space. To understand this law better, it is essential to solve some practice problems related to it. In this article, we will provide you with some Newton's first law practice problems and answers in PDF format.
Practice Problem 1
An object of mass 5 kg is at rest on a horizontal surface. What force is required to set it in motion?
To solve this problem, we need to apply the first law of motion, which states that the object at rest will remain at rest unless acted upon by an external force. Therefore, we need to apply a force that overcomes the static frictional force acting on the object. The formula for static frictional force is:
fs = μs N
where fs is the static frictional force, μs is the coefficient of static friction, and N is the normal force acting on the object.
Since the object is at rest, the normal force acting on it is equal to its weight, which is given by:
N = mg
where m is the mass of the object, and g is the acceleration due to gravity.
Substituting the values, we get:
N = 5 x 9.81 = 49.05 N
The coefficient of static friction between the two surfaces is not given. Therefore, let us assume it to be 0.2. Substituting the values in the formula for static frictional force, we get:
fs = 0.2 x 49.05 = 9.81 N
Therefore, the force required to set the object in motion is equal to the static frictional force, which is:
F = fs = 9.81 N
Practice Problem 2
An object of mass 2 kg is moving with a velocity of 5 m/s. What force is required to bring it to rest in 20 seconds?
To solve this problem, we need to apply the first law of motion, which states that an object in motion will continue to move with a constant velocity unless acted upon by an external force. Therefore, we need to apply a force that alters the object's velocity to bring it to rest.
The formula for the force required to change the velocity of an object is given by:
F = m (v − u) / t
where F is the force required, m is the mass of the object, v is the final velocity, u is the initial velocity, and t is the time taken.
Here, the initial velocity of the object is 5 m/s, and the final velocity is 0 m/s (since we need to bring it to rest). Therefore, substituting the values, we get:
F = 2 x (0 - 5) / 20 = -0.5 N
Since the force cannot be negative, it means that we need to apply a force of 0.5 N in the opposite direction to bring the object to rest.
Practice Problem 3
A body of mass 10 kg is moving with a velocity of 4 m/s. A force of 20 N is applied to it in the direction of its motion. Calculate its velocity after 5 seconds.
To solve this problem, we need to apply the first law of motion, which states that an object in motion will continue to move with a constant velocity unless acted upon by an external force. Therefore, we need to calculate the acceleration of the object due to the applied force.
The formula for acceleration is given by:
a = F / m
where a is the acceleration, F is the force applied, and m is the mass of the object.
Substituting the values, we get:
a = 20 / 10 = 2 m/s^2
Therefore, the velocity after 5 seconds can be calculated using the formula:
v = u + at
where u is the initial velocity, a is the acceleration, and t is the time taken.
Substituting the values, we get:
v = 4 + 2 x 5 = 14 m/s
Conclusion
Newton's first law of motion is a crucial concept in physics. To understand it better, it is essential to solve some practice problems related to it. In this article, we have provided you with some Newton's first law practice problems and answers in PDF format. By solving these problems, you can gain a deeper insight into the concept and its applications in the real world.
