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Flashcards by brittany99, updated more than 1 year ago
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Created by brittany99
about 10 years ago
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| Question | Answer |
| Forces are pushes or pulls. They are measured in newtons (N). Forces may vary in size and act in different directions. | When two objects interact the forces they exert on each other are equal and opposite. |
| If a number of different forces act on an object they can be replaced by a single force called the resultant force. | A resultant force acting on an object may cause a change in its state regarding rest or motion. |
| If the resultant force acting on a stationary object is zero the object won't move. If it is not zero the object will move in the direction of the resultant force. | If the resultant force acting on a moving object is zero the object will keep moving at the same speed and direction as before. If not zero the object will accelerate in the direction of the resultant force. |
| The change of an object depends on the size of the resultant force (bigger force greater acceleration) and the mass of the object (bigger mass smaller acceleration). | The relationship between force, mass and acceleration: F = m x a. F= resultant force in N. m= mass in kg. a= acceleration in m/s². |
| The speed of an object is a measure of how fast it is moving. The speed of something can be worked out if you know the distance it travels and the time it took to do so. | You can calculate speed using this simple formula: s = d ÷ t. s= speed in m/s. d= distance travelled in m. t= time taken in s. |
| Speed can also be determined from the slope or gradient of a distance-time graph. The steeper the slope the greater the speed. | The velocity of an object and the speed of an object are not the same thing. The velocity is its speed in a certain direction. |
| The acceleration of an object is the rate of which its velocity changes. It measures how quickly an object speeds up or slows down. To calculate it you need to know the change in velocity and the time taken for the change. | The acceleration equation is as follows: a = v - u ÷ t. a= acceleration in m/s². v= final velocity in m/s. u= initial velocity in m/s. t= time taken in s. |
| Deceleration is a negative acceleration. It describes an object that is slowing down. It is calculated using the same equation as for acceleration. | The velocity of an object can be represented using a velocity-time graph. The slope or gradient of a velocity-time graph gives the acceleration of an object. |
| Friction is a force that occurs when an object moves through a medium (like air or water) or when surfaces slide past each other. Friction works against the object in the opposite direction to which it is moving, its a resistive force. | The stopping distance of a vehicle depends on the thinking distance (distance travelled during the driver's reaction time) and the braking distance (distance travelled under the braking force). |
| The overall stopping distance is increased if: the vehicle is travelling at a greater speed, there are weather conditions like ice, the driver is tired or under the influence of drugs, the driver is using their mobile or the vehicle is in a poor condition. | All falling objects experience two forces- a downward force called weight, and an upward frictional force like air resistance or drag through a fluid. Weight always remains the same and it is measured in newtons (N). |
| To calculate the weight of an object the following equation is used: W = m x g. W= newtons. m= mass in kg. g= gravitational field strength in N/kg. | An object falling through the air will initially accelerate because of the force due to gravity. Eventually the resultant force will be zero as the weight and resistance forces balance. The object will move at a steady speed, its terminal velocity. |
| A force acting on an object may cause the object to change its shape. A force applied to an object when it is able to return to its original shape when the force is removed is said to be elastic. | The equation for forces and elasticity is: F = k x e. F= applied force in N. e= extension in m. k= spring constant in N/m. |
| The amount of work done, force and distance are related by the equation: W = F x d. W= work done in J. F= force applied in N. d= distance moved in the forces direction in m. | Power is the work done in a given time and is given by the equation: P = E ÷ t. P= power in w. E= energy transferred in J. t= time taken in s. |
| Gravitational potential energy can be calculated using the following equation: Ep = m x g x h. Ep= the change in GPA in J. m= mass in kg. g= G field strength in N/kg. h= height in m. | Kinetic energy can be calculated using this: Ek = 1/2 x m x v². Ek= kinetic energy in J. m= mass in kg. v= speed in m/s. |
| Momentum can be calculated using this formula: p = m x v. p= momentum in kg m/s. m= mass in kg. v= velocity in m/s. | Momentum is like velocity. It has size (magnitude) and direction. The direction of movement is vital in momentum questions. |
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