Mechanics Flashcards
State the equations for uniformly accelerated motion in one dimension: (4)
- V=U+at
- S=ut+1/2a(t^2)
- V^2=U^2+2aS
- S=((V+U)/2)t
How can data logging be used in mechanical experiments
Light gates - measuring acceleration of gravity experiment
What quantities can be derived from a:
a) displacement-time graph
b) velocity-time graph
c) acceleration-time graph
a) Velocity = ∆S/∆t (gradient)
b) Displacement = ((V+U)/2)t (area)
Acceleration = ∆V/∆t (gradient)
c) Velocity = a*t (area)
Describe the motion of a projectile moving freely under gravity with speed u:
a) vertical component/displacement
b) horizontal component/displacement
c) how are the two components linked
d) how to find greatest height achieved
e) how to find distance from start to finish
a) usinß; S=usinßt+1/2g(t^2)
b) ucosß; S=ucosßt
c) linked by time
d) to find greatest height achieved use vertical displacement; V=0
e) to find the distance from start to finish use horizontal displacement
Explain the difference between scalar and vector quantities:
Scalar - quantities which only have magnitude
Vector - quantities which have magnitude and direction
Define Centre of Gravity
Centre of gravity - the point at which the weight of the object can be said to act
Explain Newton’s first law of motion
Newton’s first law of motion states that an object will remain in a state of rest or continue to move with a constant velocity unless acted upon by a resultant external force (a=0)
Explain Newton’s second law of motion
Newton’s second law of motion states that the resultant force exerted on a body is directly proportional to the rate of change of linear momentum of the body
∑F=ma
a=∆v/∆t; momentum=p=massvelocity
F=(m∆v)/∆t; therefore F=∆mv/∆t =>
=> resultant force=change in momentum/time interval
What are the expressions for Gravitational Field Strength and Weight
F=mg; g=F/m
W=mg
Explain Newton’s third law of motion and the pairs of forces
Newton’s third law of motion states that if body A exerts a force on body B, body B will exert an equal and opposite force on body A
Newton’s third law pairs of forces must always:
- act on two separate bodies
- be of the same type
- act along the same line
- be equal in magnitude
- act in opposite directions
What’s the formula for Kinetic Energy?
KE=1/2 m(v^2); change in KE occurs only when speed changes
What’s the formula for Gravitational Potential Energy?
GPE=mg∆h
Explain Work Done and The Principle of Conservation of Energy
Work Done = Force * Distance in the direction of the force applied
W.D.=F*d
Change in total energy = Work Done by the force
If no external forces act, total energy is constant
Define Impulsive Force
Impulsive force - a very large force acting over a small period of time.
A crumple zone at the front of a car will increase the time taken for the car to come to a halt and so reduce the impulsive force thus reducing the chance of serious injury to the driver
What’s the formula for Power?
Power = Work Done / Time taken
P=Wd/t=E/t measured in Watts [W]=[J s^-1]
