SP2 - Motion and Forces Flashcards
How do you represent forces on a diagram?
Forces can be represented using free body force diagrams. Each force is represented with an arrow, which shows the direction and size of the force.
How do you calculate the resultant force of an object?
If two forces are acting in the same direction, add them. If they are acting in opposite directions, subtract them. The resultant force is the overall force acting on an object.
What are balanced and unbalanced forces?
Balanced forces are resultant forces of zero (the forces ‘cancel each other out’). Unbalanced forces are when there is a non-zero resultant force.
What is Newton’s first law of motion?
Newton’s first law states that an object in motion will remain in motion at a constant velocity and an object which is at rest will remain at rest unless a resultant force acts on it (i.e. the motion of an object will not be changed unless a non-zero resultant force is acting on it)
Explain circular motion and why objects in circular motion are said to be accelerating.
Circular motion is caused by a centripetal force, this may be gravity, tension or friction. An object moving in a circle is constantly changing direction and since acceleration is a vector quantity, even though the speed of an object in circular motion may not be changing, it is still said to be accelerating.
What is the difference between mass and weight?
Mass is the amount of matter something contains - it never changes unless the object changes.
Weight is the amount of gravity acting on an object. It is measured in Newtons (W=m x gfs) - it changes depending on the mass of the object and the strength of gravity.
Explain terminal velocity.
Terminal velocity is the maximum speed a falling object can reach. This happens because when an object first begins to fall, it’s weight acts downwards, but it doesn’t have much air resistance yet as it hasn’t been falling for long so not many collisions between air particles have happened, therefore the resultant force acts downwards. This causes the object to speed up, which increases its air resistance and therefore decreases its rate of acceleration as the resultant force is not as strong as before. Eventually, the air resistance will increase to a point where it is equal to the weight, and this point is when the object has reached terminal velocity. Their velocity will not change unless something in the environment changes (e.g. opening of a parachute).
What is Newton’s second law of motion?
Newton’s second law states that the force acting on an object depends on its mass and acceleration.
Force (N) = mass (kg) x acceleration (m/s^2)
What is inertial mass?
The more mass something has, the more force needed to change its velocity (it has strong inertia). Inertial mass is the force divided my acceleration (m=F/a).
What is Newton’s third law of motion?
Newton’s third law states that when two objects interact, the forces exerted on each one are equal and opposite.
What effect does Newton’s third law have in collisions?
When two objects collide, the forces exerted in each one are equal and opposite, however the effect on each one may not be the same because they may have different masses.
What is momentum + equation?
Momentum is a measure of the tendency of an object to keep moving - or how hard it is to stop it moving. It is a vector quantity.
Momentum (kg m/s) = mass (kg) x velocity (m/s)
How do you calculate force given change in momentum?
Force (N) = change in momentum (kg m/s) / time (s)
What is the conservation of momentum?
Conservation of momentum means that in collision, the total momentum before the collision equals the total momentum after (as long as there are no external forces acting).
What is the thinking distance?
The distance the car travels while the driver reacts to the stimulus (i.e. the distance travelled between when the driver detects the stimulus and puts the brakes on)
