MCQ
Q.
When the speed of a moving body is doubled?
Correct Answer: B
The correct answer is Its momentum is doubled.
Key Points
- Momentum is a vector quantity; it has both magnitude and direction.
- Isaac Newton’s second law of motion states that the time rate of change of momentum is equal to the force acting on the particle.
- Momentum can be calculated by multiplying the mass of an object by its forward velocity. (mv = kg*m/s).
- Mass and velocity are both directly proportional to the Momentum.
- If you increase either mass or velocity, the Momentum of the object increases proportionally.
- If you double the mass or velocity, you double the Momentum.
- If you halve the mass or velocity, you half the Momentum.
- Newton's laws of motion-
- Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force. This postulate is known as the law of inertia.
- Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion. It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it. The momentum of a body is equal to the product of its mass and its velocity.
- Newton’s third law states that when two bodies interact, they apply forces to one another equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.
Important Points
- Acceleration, the rate at which velocity changes with time in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down. Motion on a circle is accelerated even if the speed is constant because the direction is continually changing.
- Kinetic energy, a form of energy that an object or a particle has because of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and gains kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass.
- Potential energy, stored energy that depends upon the relative position of various parts of a system. Spring has more potential energy when it is compressed than stretched. A steel ball has more potential energy raised above the ground than it has after falling to Earth.
