Further Mechanics 1 Flashcards
1.1 What is the equation for momentum?
Momentum = mass x velocity
P = mv
1.1 What are the equations for impulse?
Impulse = force x time
I = Ft
Impulse = final momentum - initial momentum (aka change in momentum)
I = mv - mu
1.2 What does the conservation of momentum state? Give the formula for it
Total momentum before impact = Total momentum after impact
m1u1 + m2u2 = m1v1 + m2v2
1.3 What type of quantities are vectors?
Impulse and momentum
2.1 What is the formula for work done?
work done = component of force in direction of motion x distance moved in direction of force
W = Fs
2.1 What is the formula for work done against gravity?
work done against gravity = mgh
W = mgh
2.2 What is the formula for kinetic energy?
KE = (1/2)mv^2
2.2 What is the formula for potential energy?
PE = mgh
2.2 What is the formula for work done in terms of kinetic energy?
W = change in KE
= (1/2)m(v^2 - u^2) or (1/2)m(u^2 - v^2)
2.3 What is the conservation of energy principle?
When no external forces (other than gravity) do work on a particle during its motion, the sum of the particle’s kinetic energy and potential energy remains constant
Work in + initial KE + initial GPE = final KE + final GPE + Work out
where:
- work in = Fs
- initial & final KE = 0.5mu^2 & 0.5mv^2
- initial/final GPE = mgh
-work out = resistance x distance
2.3 What is the work-energy principle?
Change in total energy of a particle = work done on the particle
2.3 How do you calculate energy lost in a system? What does this also equal?
Energy lost = initial KE - final PE
Also:
= work done against resistance
2.3 What is the equation that links PE lost, KE gained, and work done against resistance?
PE lost = KE gained + work done against resistance
2.3 How do you work out the work done against friction?
- Find the change in KE and the change in PE
- Difference between these is work done against friction due to the conservation of energy
2.4 What is power? What is the unit?
Power is the rate of doing work
Unit is Watts (W)
2.4 What is the equation for power?
P = Fv
Power = force x velocity
(Force is the driving force of the object)
4.1 What is the coefficient of restitution?
(speed of separation of particles)/(speed of approach of particles)
e=(v2 - v1)/(u1 - u2) OR speed in x e = speed out
4.1 Why is the equation for the coefficient of restitution important?
e = (v2 - v1)/(u1 - u2)
v2 > v1 so the particles separate
u1 > u2 so the particles collide
4.1 What does it mean if the coefficient of restitution equals 0?
If e=0, then the particles ‘coalesce’ & the collision is totally inelastic
4.1 What does it mean if the coefficient of restitution equals 1?
If e=1, then the collision between particles is totally elastic (no energy is lost)
