# KS5 Dynamics

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# Dynamics & Energy - Objectives

Content

• Centre of gravity

• Turning effects of forces

• Equilibrium of forces

• Force, mass and acceleration

• Work and Energy

• Power

• Motive power

Learning Outcomes

Candidates should be able to:

• demonstrate an understanding that mass is the property of a body which resists change in motion.
• recall and apply Newton's three laws of motion in appropriate situations.
• recall and use the equation F = ma, in situations where mass is constant, appreciating that force and acceleration are always in the same direction.
• construct and use free-body diagrams.
• describe and use the concept of weight as the effect of a gravitational field on a mass
• recall and use the relationship weight = mass x gravitational field strength.
• understand that the weight of a body may be taken as acting at a single point known as its centre of gravity.
• know that the position of the centre of gravity of a uniform regular solid is at its centre.
• define the moment of a force about a point as the force x the perpendicular distance from the point to the line of action of the force.
• understand a couple as a pair of equal and opposite coplanar forces tending to produce rotation only.
• define the moment of a couple (torque) as the magnitude of one of the forces x the perpendicular distance between the lines of action of the forces.
• undertand that, for an object in rotational equilibrium, the sum of the clockwise moments will equal the sum of the anticlockwise moments.
• show an understanding that, when there is no resultant force and no resultant moment, a system is in equilibrium
• apply the principle of moments to solve problems involving forces acting in two dimensions.
• understand the concept of work in terms of the product of force and displacement in the direction of the force.
• deal with quantitative and qualitative questions involving variable forces
• appreciate the significance of the area under a force-displacement graph.
• undestand that the work done is equal to the energy transferred.
• recall and use the equation W = Fscosθ, where F is a constant force along the direction of motion.
• recall and use equations for kinetic energy Ek = ½ mv2 and change in gravitational potential energy ΔEp = mgΔh.
• understand the principle of conservation of energy and apply it to examples involving kinetic energy, gravitational potential energy and work done against resistive forces.
• relate power to work done and time taken.
• recall and use the equation W = Pt.
• recall and use the relationship motive power = driving force x speed.
• calculate and express efficiency of a system as a number or percentage.
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