Physics · Laws Of Motion · NEET
Momentum is a vector. Since p = mv and mass m is a positive scalar, p points in the exact same direction as the velocity v. This is why NEET asks about the DIRECTION of momentum, not just its size. A ball moving east has eastward momentum; the same ball moving west has westward momentum (opposite sign).
Velocity tells you how fast and in which direction a body moves. Momentum also includes the mass: p = mv. Two bodies can have the same velocity but different momentum if their masses differ. A loaded truck and a small car moving at the same speed have very different momentum because the truck has much more mass.
The SI unit is kilogram metre per second, written kg m/s. You get it by multiplying mass (kg) by velocity (m/s). There is no special name for this unit. It can also be written as newton-second (N s), because 1 N s = 1 kg m/s.
Yes. Momentum is mass times velocity, so a small mass with a high velocity can match a large mass with a low velocity. Example: a 2 kg body at 10 m/s has p = 20 kg m/s, and a 20 kg body at 1 m/s also has p = 20 kg m/s. This is a common NEET idea used in collision and recoil problems.
Yes. Momentum is a vector, so a change in direction is a change in momentum even if the speed (magnitude) is constant. A body moving in a circle at constant speed has constant momentum magnitude but its momentum direction keeps changing, which is why a force (centripetal) is needed. This is a favourite NEET trap.
A football player moving southward suddenly turns eastward with the same speed to avoid an opponent. The force that acts on the player while turning is directed:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Linear momentum is how much motion a body has. It is found by multiplying mass by velocity, p = mv. A heavier or faster body has more momentum, and it is harder to stop.
The formula is p = mv, where m is mass in kg and v is velocity in m/s. Because velocity is a vector, momentum is also a vector pointing the same way as the velocity.
The SI unit is kg m/s (also written N s). The dimensional formula is [M L T^-1].
Newton's second law is really about the rate of change of momentum, and conservation of momentum solves collisions, recoil, and explosion problems. Getting momentum's vector direction right is needed for many NEET questions and connects directly to the next topic, Newton's second law.
No. Inertia is a body's resistance to change in its motion and depends only on mass. Momentum depends on both mass and velocity, and it is a vector. A body at rest has inertia but zero momentum.
