ODU Flashcards
State the definition of acceleration
acceleration is the rate of change of velocity
the gradient of an s-t graph gives…
velocity
the gradient of a v-t graph gives…
acceleration
the area under a v-t graph gives…
displacement
the area under an a-t graph gives…
velocity
how do you know that the vector on a motion-time graph has started acting in the opposite direction?
The graph crosses the time axis
explain satellite motion
the satellite is in freefall around a planet. It follows a circular path because it has a constant velocity at a tangent to the planet and a constant acceleration towards the planet. The projectile does not it the planet because it has velocity at a tangent to the planet’s surface.
Projectiles have constant horizontal ________ and constant vertical ________ in the absence of friction
Projectiles have constant horizontal velocity and constant vertical acceleration in the absence of friction
Always consider _______ and ________ components separately
Always consider horizontal and vertical (i.e. perpendicular) components separately
state newton’s first law
newton’s first law states that an object at rest will remain at rest and an object in motion will remain in motion with constant velocity unless acted upon by an unbalanced force
State a corollary of newton’s first law (just checking you know the implications of newton 1)
an object will accelerate when acted upon by an unbalanced force
state what is meant by the phrase “balanced forces”
forces have the same size but opposite direction (i.e. there is no net force on an object)
state newton’s second law
the vector sum of forces on an object is equal to the product of the mass and acceleration of an object i.e. ΣF = ma
State newton’s third law
Every action force has an equal and opposite reaction force. Remember: The action and reaction force act on different objects. Newton 3 applies to interaction between objects
state what is meant by “friction”
Friction is a force which opposes the motion of an object
state what is meant by “tension”
Tension is a force which is transmitted from one object to another via a coupling. It acts in opposite directions on each object
State what is meant by “terminal velocity”
terminal velocity is the maximum velocity of an object in freefall when friction is taken into account. It happens when weight = -friction
What does the reading on a scale calibrated in newtons tell you?
the normal reaction force
Explain why the reading on a scale changes when in a lift
w = mg acts downwards and doesn’t change. N is the normal reaction force. This changes depending on the acceleration of the lift: ΣF = ma => N-mg = ma. The scales show N.
State the equation for calculating the component of an object’s weight acting down a slope
mgsin(θ)
State the equation for calculating the component of an object’s weight perpendicular to a slope
mgcos(θ)
State the law of conservation of momentum
The total momentum before a collision/explosion is equal to the total momentum after a collision/explosion in the absence of external forces
State what is meant by the term “elastic collision”
Both kinetic energy and momentum are conserved
State what is meant by the term “inelastic collision”
Momentum is conserved but kinetic energy is not