# Dynamics and Equilibrium - Physics Learning 3

Learn Dynamics and Equilibrium questions with answers. This prep guide includes questions like, what is 1n?, what is difference between mass and weight?, what is force which causes rocket to take off?, why fragile objects are packed inside polyethylene sheets?, why is it advised to wear seatbelts? and others below.

## Dynamics and Equilibrium Learning 3

Question: What is 1N?

Answer: The SI unit of force is newton (N). It is defined as the force which produces an acceleration of 1 ms-2 in a body of mass 1 Kg. Mathematically, 1N = 1 Kg 1 ms-2.

Question: What is difference between mass and weight?

Answer: Quantity of matter present within a body is called mass. It's SI units are Kg. It is scalar quantity and remains same on changing the distance of object from center of earth. The force with which the earth attracts the body towards it's center is called weight. It's SI units are N. It is a vector quantity and it varies as we change the distance of object from the center of earth.

Question: What is force which causes rocket to take off?

Answer: Taking off of rocket is an example of newton's 3rd law of motion, which states that; action and reaction are equal in magnitude but opposite in direction. The rocket takes off vertically. The fuel and hot gases escape out of rocket's tail with high pressure, this is an action. As a result of propelling force of these gases, rocket moves up, which is the reaction equal in magnitude and opposite in direction.

Question: Why fragile objects are packed inside polyethylene sheets?

Answer: Fragile objects such as glass wares are packed in polyethene sheets and Styrofoam rings because these materials provide large impact time during any mishap. An increase in impact time decreases the rate of change of momentum and hence lessens the impact of force which in turn decreases the damage caused due to accident.

Question: Why is it advised to wear seatbelts?

Answer: Wearing seatbelts while driving prevents the damage caused to driver in case of any accidents. Seatbelts provide an external force to the driver and in case of an accident seatbelts helps prolong the impact time for momentum to change and thus the effects of accident are reduced.