Equilibrium and Momentum

Question 1

Equilibrium

Answer 1

When something is in equilibrium, the vector sum of all forces acting on it = 0.
It moves with constant velocity.

Question 2

Unit for force

Answer 2

kg m / s²

Question 3

Translational Equilibrium

Answer 3

When things are at translational equilibrium, the vector sum of all forces = 0.

Question 4

Translational Equilibrium for an incline

Question 5

Rotational Equilibrium

Answer 5

When things are at rotational equilibrium, the sum of all torques = 0.

Question 6

Positive and Negative torques

Answer 6

Conventionally, positive torques act counterclockwise, negative torques act clockwise.

Question 7

Newton’s First Law on Equilibrium

Answer 7

The significance of Newton’s first law on equilibrium is: things in equilibrium will remain in equilibrium unless acted on by an external force.

Question 8

Newton’s First Law on Momentum

Answer 8

The significance of Newton’s first law on momentum is: things resist change in momentum because of inertia (try stopping a truck. It’s not easy because it resists changes to its huge momentum).

Question 9

Torque

Answer 9

Torque is the angular equivalent of force - it makes things rotate, have angular acceleration, change angular velocity and direction.

Question 10

Lever

Answer 10

The lever arm consists of a lever (rigid rod) and a fulcrum (where the center of rotation occurs): F₁L₁ = F₂L₂

Question 11

If you apply a force at a long distance from the fulcrum….

Answer 11

you exert a greater force on a position closer to the fulcrum

Question 12

Real Weightlessness

Answer 12

when there is no net gravitational force acting on you. Either you are so far out in space that there’s no objects around you for light-years away, or you are between two objects with equal gravitational forces that cancel each other out.

Question 13

Apparant Weightlessness

Answer 13

this is what we “weightlessness” really means when we see astronauts orbiting in space. The astronauts are falling toward the earth due to gravitational forces (weight), but they are falling at the same rate as their shuttle, so it appears that they are “weightless” inside the shuttle.

Question 14

Momentum

Answer 14

Momentum = mv, where m is mass, v is velocity and the symbol for momentum is p.

Question 15

Impulse

Answer 15

• Impulse = Ft, where F is force and t is the time interval that the force acts.
• Impulse = change in momentum

Question 16

Conservation of Linear Momentum

Answer 16

Total momentum before = total momentum after.

Question 17

Elastic Collisions

Answer 17

Perfectly elastic collisions: conservation of both momentum and kinetic energy.

Question 18

Inelastic Collisions

Answer 18

Conservation of momentum only.

Kinetic energy is lost during an inelastic collision.