Forces & Motion Flashcards
(33 cards)
1
Q
What is a scalar?
A
- A quantity that has magnitude only
2
Q
What is a vector?
A
- A quantity that has magnitude and direction
3
Q
What is the moment (or torque) of a force about a pivot?
A
- Force x the perpendicular distance from the pivot to the line of action of the force
4
Q
What is the principle of moments?
A
- For a system to be in equilibrium, sum of anticlockwise moments about a pivot = sum of clockwise moments about the same pivot
5
Q
What is the centre of gravity?
A
- The single point within a body at which the entire weight of the body is considered to act
6
Q
What is the displacement of a point B from a point A?
A
- The shortest distance from A to B, together with the direction
- Measured in m
7
Q
What is average speed?
A
- Total distance travelled ÷ total time taken
- Measured in m/s
8
Q
What is instantaneous speed?
A
- Rate of change of distance
- Measured in m/s
9
Q
What is average velocity?
A
- Total displacement ÷ total time taken
- Measured in m/s
10
Q
What is velocity?
A
- Rate of change of displacement
- Measured in m/s
11
Q
What is average acceleration?
A
- Change in velocity ÷ time taken
- Measured in m/s²
12
Q
What is acceleration?
A
- Rate of change of velocity
- Measured in m/s²
13
Q
What is momentum?
A
- p = mv
- Vector
- Measured in kg m/s
14
Q
What is mass?
A
- A measure of the amount of substance (matter) in an object
15
Q
What is gravitational field strength (g)?
A
- The force experienced per unit mass by a mass placed in the field
- Measured in N/kg
16
Q
What is weight?
A
- The force that acts upon an object due to its position in a gravitational field
17
Q
What is resultant force?
A
- When the forces acting on an object are unbalanced, causing the object to accelerate
18
Q
What is Newton’s 1st Law of Motion?
A
- An object continues in a state of uniform motion in a straight line, or remains at rest, unless acted upon by a resultant force
19
Q
What is Newton’s 2nd Law of Motion?
A
- The acceleration of an object of constant mass is directly proportional to the resultant force acting on it
- F = ma
20
Q
What is Newton’s 3rd Law of Motion?
A
- If an object A exerts a force on a second object B then B must exert a force which is equal in magnitude but opposite in direction on A
21
Q
What is elastic behaviour?
A
- Ability of a material to recover its original shape after the external force is removed
22
Q
What is Hooke’s Law?
A
- The extension of an object such as a wire or spring is directly proportional to the stretching force or tension, provided the elastic limit is not exceeded
- F = k(constant)x
23
Q
What is friction?
A
- A force that acts between two surfaces that resists motion between the surfaces
24
Q
What is terminal velocity?
A
- The constant, maximum velocity of an object when the resistive forces on it are equal and opposite to the accelerating forces (e.g. pull of gravity)
25
How is extension calculated?
- Stretched length - Original length
26
What is the spring constant?
- The spring constant (k) is the force per unit extension
- Measured in N/m
27
What is efficiency?
- Useful output work or energy ÷ Input work or energy x 100
28
What is the conservation of momentum?
- Sum of momentum before a collision or explosion = sum of momentum after, provided no external force is acting
29
What is the centre of mass?
- Point where all the mass of a body can be considered to act
30
How is change of momentum calculated?
- Impulse (= Force x time)
31
How to get speed from a distance-time graph?
- Gradient
32
How to get distance from a speed-time graph?
- Area under the curve
33
What does the gradient of a velocity-time graph represent?
- The acceleration
