mechanics Flashcards
1) How is momentum calculated?
Momentum (kg ms^-1) = mass (kg) x velocity (ms^-1)
1) What is impulse? (2)
A change in momentum
The impulse of body B on body A = the impulse of body A on body B
1) How is impulse calculated? (2)
I = mv - mu (final momentum - initial momentum) I = Ft (force x time)
1) What is conservation of linear momentum? (2)
If two objects moving in a straight line collide, the momentum before the collision = the momentum after the collision
m1u1 + m2u2 = m1v1 + m2v2
4) What is Newton’s experimental law?
In direct collisions the relative velocity of the two bodies is reversed and the speed of separation is e times the speed of approach
4) What is e? (2)
The coefficient of restitution
A constant for two surfaces in contact that is dependent on the nature of the two surfaces where 0 < e < 1
4) How is e calculated? (2)
|speed of separation| / |speed of approach|
The speeds of objects moving in the same direction («_space;or»_space;) are subtracted whilst the speeds of objects moving in opposite directions (<> or >
2) What is kinetic energy? (2)
The energy of a particle due to its motion
KE = 1/2 mv^2
2) How is loss in kinetic energy calculated?
Total KE before collision - Total KE after collision
2) How is work done calculated?
Work done = force in direction of motion x distance moved
2) How is work done against gravity calculated?
Work done = mass x g x vertical height difference
2) What is potential energy?
PE = mgh
2) How are work done and kinetic energy connected?
Work done = change in kinetic energy
2) What is the principle of conservation of mechanical energy?
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
2) What is the work-energy principle?
The change in total energy of a particle is equal to the work done on the particle
