1.3 Dynamics

Question 1

Force, F

Answer 1

A force on a body is a push or a pull acting on the body from some external body. Unit: N

Question 2

Newton’s 3rd Law

Answer 2

If a body A exerts a force on a body B, then B exerts an equal and opposite force on A.

Question 3

ΣF=ma

Answer 3

The mass of a body × its acceleration is equal to the vector sum of the forces acting on the body. This vector sum is called the resultant force.

Question 4

Momentum

Answer 4

The momentum of an object is its mass multiplied by its velocity. (p = mv). It is a vector.
UNIT: kg m s-1 or Ns

Question 5

Newton’s 2nd law

Answer 5

The rate of change of momentum of an object is proportional to the resultant force acting on it, and takes place in the direction of that force.

Question 6

The principle of conservation of momentum

Answer 6

The vector sum of the momenta of bodies in a system stays constant even if forces act between the bodies, provided there is no external resultant force.

Question 7

Elastic collision

Answer 7

A collision in which there is no change in total kinetic energy.

Question 8

Inelastic collision

Answer 8

A collision in which kinetic energy is lost.