AQA AS Level Physics - Unit 2 2021/2022

Scalar A physical quantity with magnitude only. Speed Change of distance per unit time. Acceleration Change in velocity per unit time. Vector A physical quantity with magnitude and direction. Displacement The distance in a given direction. Velocity Speed in a given direction or the change in displacement over time Resultant The force which results from two or more forces acting on the same particle. Moment Moment of a force about a point defined as force × perpendicular distance from the point to the line of Principle of moments The sum of the clockwise moments is equal to the sum of the anticlockwise moments. Centre of mass The point on a object through which a single force on the body has no turning effect. Uniform A body is uniform if it's mass is evenly distributed along its length. Couple A couple is a pair of equal and opposite forces acting on a body, but not along the same line. Upgrade to remove ads Only $35.99/year Terminal velocity The maximum speed reached by an object at which the drag force is equal and opposite to the forcce causing the motion of the object. Thinking distance The distance travelled by a car in the time it takes the driver to react. Braking distance The distance travelled by the car in the time it takes to come to a stop safely. Stopping distance The distance travelled in both the thinking and braking distances. Vehicle Bumpers They give way in a collision, which increases the impact time of a collision and thus reduces the resultant force on a passenger. Crumple zones The engine compartment crumples under a front end impact to increase the impact time and thus reduce the resultant force. Seat belts Restrain the wearer from crashing into the vehicle frame during a sudden change in momentum and brings them to halt more slowly, increasing the impact time and thus reducing the reulstant force. Collapsible steering wheel Increases the impact time by collapsing when contacted by the drive, reducing the resultant force on the driver in the impact. Air bags Increases the impact time and the area over which the resultant force acts, decreasing the pressure and force on the passanger. Principle of the conservation of energy Energy cannot be created or destroyed. Upgrade to remove ads Only $35.99/year Work done Force multiplied by the distance moved in the direction of the force. Kinetic Energy The energy of an object due to its motion. Power The rate of transfer of energy. Efficiency The work done over the total energy supplied. Density The mass per unit volume of a substance. Hooke's Law States that the force needed to stretch a spring is directly proportional to the extension of the spring from its naturual length up to the limit of proportionality. Elastic Limit The point beyond which the a wire is permanently stretched/deformed Elasticity The property of a solid that enables it to regain its shape after it has been deformed or distorted. Tensile Deformation that stretches an object. Compressive Deformation that compresses an object. Upgrade to remove ads Only $35.99/year Tensile stress The tension over the cross sectional area of the wire. It's unit is the Pascal. Tensile Strain The increase in length of the wire over the original length. It has no unit because it is a ratio. Limit of Proportionality The limit beyond which, when a wire or spring is stretched, its extension is no longer proportional to the force that stretches it. Young's Modulus Tensile stress over tensile strain. Ultimate Tensile Stress Also known as the breaking stress, the ultimate tensile stress is the stress needed to break a solid or material. Brittle A brittle material snaps without any noticeable yield. Ductile A ductile material can be drawn into a wire. Mechanical Waves Waves which move through a substance via vibrating particles. Electromagnetic Waves Vibrating electric and magnetic fields that progress through space without the need for a substance. They all travel at the speed of light.