Terms to memorise Flashcards Preview

Mechanics - physics year 1 > Terms to memorise > Flashcards

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

What is the efficiency of a machine?

Useful energy transferred by machine/ Energy supplied to the machine or power out / power in.