Flashcards in Terms to memorise Deck (32):

1

## What is a vector

### A physical quantity which has a direction as well as a mganitude.

2

## What is a scalar

### A physical quantity which has no direction

3

## Give 3 vectors

### acceleration, velocity, force

4

## What is a moment?

### The force * the perpendicular distance from the line of action of the force to the point

5

## What is principle of moments?

### For a body in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments.

6

## What is the centre of mass?

### The point at which the mass is concentrated in an object. Single force acting at centre of mass has no turning effect, as it's where gravity acts.

7

## What is a couple?

### A pair of equal and opposite parallel forces acting on the same body but not along the same line.

8

## What conditions must be attained for body to be in equilibrium?

### Resultant force must be zero and principle of moments must apply.

9

## When does toppling occur?

### When the centre of mass of an object lies outside of its base.

10

## What is velocity?

### Speed in a given direction.

11

## What is Newton's first law?

### An object either stays at rest or moves with constant velocity unless acted on by a resultant force

12

## What is Newton's second law?

### F = MA.

13

## What is Newton's third law?

### For every force there is an equal and opposite force.

14

## What is the key idea of free fall?

### Only gravity is acting on the object. Constant acceleration = g.

15

## What is gradient of displacement time graph?

### Velocity

16

## What is area under velocity time graph and what is the gradient?

### Area = displacement and gradient = acceleration.

17

## What is area under acceleration time graph?

### Change in velocity

18

## What is a projectile?

### Any object acted upon only by gravity?

19

## What is difference between friction and drag?

### Friction is a force that opposes motion when moving on a solid. Drag opposes motion in a liqud. It increases with speed.

20

## How does air resistance act against a projectile?

### Air resistance increases with speed. It has a horizontal component which reduces horizontal resultant force and therefore reduces horizontal speed and its range. Also has a vertical component which reduces maximum height and makes descent steeper than its ascent.

21

## What is the key idea of pulleys?

### Tension and acceleration is the same on either side of the pulley, as string is inextensible. Use simultaneous equations for these problems.

22

## What is unit of momentum?

### kgms^-1

23

## What is the momentum principle?

### In a closed system with no external forces acting, total momentum before = total momentum afterwards.

24

## What is an elastic collision?

### One in which no kinetic energy is lost?

25

## What is an inelastic collision?

### One in which kinetic energy is lost to the surroundings for example to deform an object or loss as thermal energy. Occurs when two objects couple together.

26

## What is energy measured in?

### Joules.

27

## What is the principle of conservation of energy?

### Energy can never be created or destroyed, only transferred.

28

## When is work done on an object.

### When a force acting on the object makes it move.

29

## When is no work done?

### When the force acts at right angles to the direction of motion.

30

## What is power defined as?

### The rate of transfer or energy or the rate of doing work.

31

## What is formula for power?

### E/T, W/T or P = FV

32