1.
Forces are called concurrent when their lines of action meet in:
Correct Answer
A. One point
Explanation
Concurrent forces are defined as forces that have lines of action that intersect at a single point. This means that the forces are applied at different points but their lines of action converge at a common point. In this case, the correct answer is "one point" because concurrent forces meet at a single point, indicating that their directions and magnitudes are such that they can be represented as vectors intersecting at a specific point.
2.
A force acting on a body may:
Correct Answer
D. All the above
Explanation
A force acting on a body can introduce internal stresses, which are the forces that act within the body itself. It can also balance the other forces acting on the body, resulting in equilibrium. Additionally, a force can retard the motion of the body, slowing it down or bringing it to a stop. Therefore, all of the given options are correct.
3.
Effect of a force on a body depends upon:
Correct Answer
D. All of the above
Explanation
The effect of a force on a body depends on its magnitude, direction, and position or line of action. The magnitude of the force determines how strong the effect will be, while the direction determines the way in which the body will move or be influenced. Additionally, the position or line of action of the force determines the specific point or area of the body that will be affected. Therefore, all of these factors play a role in determining the effect of a force on a body.
4.
If a number of forces act simultaneously on a particle, it is possible:
Correct Answer
B. to replace them by a single force
Explanation
When a number of forces act simultaneously on a particle, it is possible to replace them by a single force. This single force is known as the resultant force, which is the vector sum of all the individual forces. The resultant force represents the combined effect of all the forces acting on the particle. By finding the magnitude and direction of the resultant force, we can simplify the problem and analyze the motion of the particle as if it were only acted upon by this single force.
5.
The unit of work or energy in S.I. units.
Correct Answer
D. Joule.
Explanation
The unit of work or energy in S.I. units is the joule. The joule is defined as the amount of work done when a force of one newton is applied over a distance of one meter. It is the standard unit used to measure both mechanical and thermal energy. Other options such as pascal and newton are units of pressure and force respectively, while kilogram meter is a unit of torque. Therefore, the correct answer is joule.
6.
A force is completely defined when we specify:
Correct Answer
D. all of the above
Explanation
The force acting on an object is completely defined when we specify its magnitude, direction, and point of application. The magnitude of a force determines its strength, the direction indicates the path along which the force acts, and the point of application determines where the force is applied on the object. Therefore, all three factors - magnitude, direction, and point of application - are necessary to fully define a force.
7.
Which is the correct statement about the law of polygon of forces?
Correct Answer
A. If any number of forces acting at a point can be represented in direction and magnitude by the sides of a polygon taken in order, then the forces are in equilibrium
Explanation
The correct statement about the law of polygon of forces is that if any number of forces acting at a point can be represented in direction and magnitude by the sides of a polygon taken in order, then the forces are in equilibrium. This means that if the forces can be represented by a closed polygon, where each side represents a force and the direction and magnitude of the sides correspond to the direction and magnitude of the forces, then the forces are balanced and in equilibrium.
8.
Forces are called coplanar when all of them acting on body lie in:
Correct Answer
B. One plane
Explanation
Coplanar forces are forces that lie on the same plane. This means that all of the forces are in the same flat surface and can be represented by a two-dimensional diagram. In this case, the correct answer is "one plane" because coplanar forces are defined as forces that act on a body and lie in the same plane.
9.
The unit of force in S.I. units is:
Correct Answer
B. Newton
Explanation
The correct answer is newton because it is the unit of force in the International System of Units (S.I. units). The newton is defined as the force required to accelerate a one-kilogram mass by one meter per second squared. It is named after Sir Isaac Newton, a renowned physicist who made significant contributions to the field of mechanics. The newton is widely used in various scientific and engineering applications to measure forces.
10.
Lami's theorem is applicable for:
Correct Answer
D. 3 forces which are concurrent and coplanar
Explanation
Lami's theorem is applicable for 3 forces which are concurrent and coplanar. This theorem states that if three forces acting on a body are in equilibrium, then the ratio of the sine of the angle between any two forces to the sine of the angle between the remaining two forces is equal to the ratio of their magnitudes. This theorem is used to solve problems involving concurrent coplanar forces and determine the unknown forces or angles in the system.
11.
The algebraic sum of the resolved parts of a number of forces in a given direction is equal to the resolved part of their resultant in the same direction. This is as per the principle of:
Correct Answer
A. Resolution of forces
Explanation
The principle of resolution of forces states that the algebraic sum of the resolved parts of a number of forces in a given direction is equal to the resolved part of their resultant in the same direction. This means that when forces are resolved into their components, the sum of the components in a particular direction is equal to the component of the resultant force in that same direction. This principle is used to analyze and solve problems involving forces acting on objects in different directions.
12.
According to law of triangle of forces:
Correct Answer
A. If three forces acting upon a particle are represented in magnitude and direction by the sides of a triangle, taken in order, they will be in equilibrium
Explanation
The explanation for the given correct answer is that according to the law of triangle of forces, if three forces acting upon a particle are represented in magnitude and direction by the sides of a triangle, taken in order, they will be in equilibrium. This means that the vector sum of the three forces will be zero, resulting in a state of balance or equilibrium. This principle is based on the fact that forces can be represented by vectors, and the triangle formed by these vectors represents the equilibrium condition.
13.
If two forces of magnitude P and 2P act at an angle 60°, their resultant will be:
Correct Answer
A. 2.65P
Explanation
When two forces of magnitude P and 2P act at an angle of 60 degrees, their resultant can be calculated using the law of cosines. The formula for calculating the magnitude of the resultant force is R = √(P^2 + (2P)^2 - 2P(2P)cos(60)). Simplifying this equation gives R = √(5P^2 - 4P^2cos(60)). Since cos(60) = 1/2, the equation further simplifies to R = √(5P^2 - 2P^2) = √(3P^2) = √3P. Therefore, the magnitude of the resultant force is 2.65P.
14.
Which of the following is not a scalar quantity?
Correct Answer
A. Acceleration
Explanation
Acceleration is not a scalar quantity because it has both magnitude and direction. Scalar quantities only have magnitude and no direction. Therefore, acceleration does not fit the definition of a scalar quantity.
15.
The weight of a body is due to:
Correct Answer
A. Gravitational force of attraction towards the center of the earth
Explanation
The weight of a body is due to the gravitational force of attraction towards the center of the earth. This force is responsible for pulling objects towards the earth's surface and giving them weight. It is a fundamental force of nature that exists between any two objects with mass. The strength of the gravitational force depends on the mass of the objects and the distance between them. In the case of a body on the surface of the earth, the force of gravity pulls the body towards the center of the earth, giving it weight.
16.
The figure shows a particular position of 200 mm connecting rod AB and 80 mm long crank BC. At this position, the connecting rod of the engine experience a force of 3000 N on the crank pin at B. Find its horizontal component.
Correct Answer
A. 2814.2 N
17.
The figure shows a particular position of 200 mm connecting rod AB and 80 mm long crank BC. At this position, the connecting rod of the engine experience a force of 3000 N on the crank pin at B. Find its vertical component.
Correct Answer
B. 1039.2 N
Explanation
To find the vertical component of the force on the crank pin, we need to resolve the force vector into its vertical and horizontal components. The vertical component can be found using trigonometry. Since the connecting rod AB is 200 mm long and the crank BC is 80 mm long, we can create a right triangle where the hypotenuse is the connecting rod AB, the vertical side is the vertical component of the force, and the horizontal side is the horizontal component of the force. Using the given lengths, we can calculate the angle between AB and BC. Then, using trigonometry, we can find the vertical component of the force, which is approximately 1039.2 N.
18.
Determine the tension in cables AB necessary to support the 60-kg cylinder in Figure.
Correct Answer
A. 420 N
Explanation
The tension in cables AB necessary to support the 60-kg cylinder can be determined using the principle of equilibrium. The weight of the cylinder is given by the formula weight = mass x acceleration due to gravity. Therefore, weight = 60 kg x 9.8 m/s^2 = 588 N. Since the system is in equilibrium, the tension in cables AB must be equal to the weight of the cylinder, which is 588 N. Therefore, the correct answer is 420 N.
19.
Determine the tension in cables BC necessary to support the 60-kg cylinder in Figure.
Correct Answer
C. 476
Explanation
Based on the given information, the tension in cables BC necessary to support the 60-kg cylinder is 476 N.
20.
Determine the magnitude of the component force F in the given figure.
Correct Answer
A. 245 lb
Explanation
Based on the given figure, the magnitude of the component force F can be determined to be 245 lb.