#10 Forces and Acceleration

What is a force diagram?

A diagram that shows all the forces acting on an object

State all the forces acting on a person leaning against a wall.

Friction (with the wall and the floor)

Normal contact (with the wall and the floor)

Weight

Pushing force against the wall

State Newton’s first law of motion.

An object at rest will stay at rest and an object moving at a constant velocity will continue at a constant velocity unless acted on by a resultant force

If an object has a resultant force, what will happen to it?

It will accelerate (in the same direction as the resultant force)

When is an object said to be in equilibrium?

When it has no resultant force acting on it

Is a force a vector or a scalar and why?

Vector as it has size and direction

What two ways can a vector be written?

i + j notation or as a column vector

How do you find a resultant force from vectors?

Add them together

State Newton’s second law of motion.

The force needed to accelerate a particle is equal to the product of the mass of the particle and the acceleration produced

State the equation for the motion of a particle.

F = ma

What is the force of gravity on a body vertically downwards (on earth)?

9.8ms^-2

State the equation for weight.

W = mg

State Newton’s third law of motion?

For every action there is an equal and opposite reaction

What assumptions are made when modelling forces with a pulley?

The particles are connected by a light inextensible string

The pulley is smooth

What force is the same on both sides of a pulley?

Tension

In terms of vertical motion, what happens when particles of different weights are suspended over a pulley?

The heavier particle will pull itself down, and the lighter one will move upwards