Dynamics
Definitions: Dynamics
- One exam question, the mark-scheme answer, and the exact phrases that score (highlighted, then listed below in the same colour).
Exam question
State Newton's first law of motion.
Model answer
An object stays at rest or moves at constant velocity unless a resultant force acts on it.
Marking points
1 mark each- 1stays at rest or moves at constant velocity unless a resultant force acts on it(1)
Exam question
State Newton's second law of motion.
Model answer
The resultant force is proportional to the rate of change of momentum.
Marking points
1 mark each- 1resultant force is proportional to the rate of change of momentum(1)
Exam question
State Newton's third law of motion.
Model answer
When two bodies interact, the forces they exert on each other are equal in magnitude and opposite in direction (on two different bodies).
Marking points
1 mark each- 1equal in magnitude and opposite in direction (on two different bodies)(1)
Exam question
State what is meant by the mass of an object.
Model answer
Mass is the object's resistance to a change in motion.
Marking points
1 mark each- 1resistance to a change in motion(1)
Exam question
State what is meant by the weight of an object.
Model answer
Weight is the gravitational force on the object.
Marking points
1 mark each- 1gravitational force on the object(1)
Exam question
Define linear momentum.
Model answer
Linear momentum is the product of mass and velocity.
Marking points
1 mark each- 1product of mass and velocity(1)
Exam question
State the principle of conservation of momentum.
Model answer
The total momentum of a system is constant, provided no resultant external force acts.
Marking points
1 mark each- 1total momentum of a system is constant(1)
- 2no resultant external force acts(1)
Exam question
State what is meant by a perfectly elastic and by an inelastic collision.
Model answer
Perfectly elastic: total kinetic energy is conserved. Inelastic: total kinetic energy decreases.
Marking points
1 mark each- 1kinetic energy is conserved(1)
- 2kinetic energy decreases(1)