UNIT1 - dynamics

Question 1

What is the difference between a scalar and a vector?

Answer 1

SCALAR is a physical quantity with ONLY MAGNITUDE.

VECTOR is a physical quantity with MAGNITUDE AND DIRECTION.

Question 2

What are some scalar quantities?

Answer 2

Speed
Temperature 
Energy
Mass
Distance
Time

Question 3

What are some vector quantities?

Answer 3

Displacement
Velocity
Acceleration
Force

Question 4

What is speed and what are it’s units?

Answer 4

Speed is how fast a body is travelling.

Metres per second.

Question 5

What is energy, what forms can it be in and what are it’s units?

Answer 5

The capacity for doing work.
Kinetic, potential, thermal, electrical, chemical or nuclear.
Joules

Question 6

What is the difference between distance and displacement?

Answer 6

Distance is how far a body has travelled.

Displacement is how far a body has traveled in a direction from its origin.

Question 7

What is velocity?

Answer 7

A measure of a body’s speed and direction.

Question 8

What is acceleration and what are it’s units?

Answer 8

Acceleration is the speed gained by a body every second OR rate of change of velocity of a body with respect to time.
Metres per second per second.

Question 9

What is a force and what are it’s units?

Answer 9

An interaction with a body that causes a change in the motion of the body.
Newtons.

Question 10

A car travels 20km East and then 30km West.

What is the cars displacement?

Answer 10

Draw vector diagram TO SCALE.
State displacement.

Answer: 10km West

Question 11

A car travels 50km West and 70km South.

What is the cars displacement?

Answer 11

METHOD 1 - use pythagoras
METHOD 2 - draw diagram TO SCALE, using ruler measure resultant vector and then use protractor from North to get degrees for direction.

Answer: 86.02km (plus degrees)

Question 12

What are the 3 formulas concerning

• speed/velocity (v)
• distance (d)
• displacement (s)
• time (t)

Answer 12

S=v x t

S=average v x t

D= average v x t

Question 13

Describe an experiment to measure average speed.

Answer 13

A small vehicle is placed on a slope, we measure slope and measure from back of vehicle its total distance travelled.
We time how long it takes to go down the slope.
Repeat 3 times.
Using average time calculate speed by dividing distance by time.

Question 14

Describe an experiment to measure instantaneous speed.

Answer 14

A small vehicle with a small bit of card attached at the top is placed on a slope. A light gate is connected to a QED meter as a timer. This times the vehicle as it goes through the light gate.
We then divide the length of the card by the time measured by the light gate.

Question 15

How do we calculate acceleration?

Answer 15

A=(v-u)/t

(Final speed-initial speed) ÷ time

Question 16

Describe an experiment to measure acceleration.

Answer 16

A small vehicle with a small bit of card attached to the top is placed on a slope. As it travels it passes through 2 light gates connected to a timer giving us our 2 values for speed. We also measure time between gates.

Question 17

What is Newtons first law?

Answer 17

A body at rest or moving in a straight line with a constant velocity will continue to be at rest or continue to move in a straight line unless acted on by an unbalanced force.

Question 18

What is Newtons second law

Answer 18

The acceleration of a body is directly proportional to the unbalanced force acting on the body. (straight line from origin increasing)
F1/F2=A1/A2
The acceleration of a body is inversely proportional to its mass. (line from high on y axis curving down)
A1/A2=M2/M1

Question 19

What is Newtons third law?

Answer 19

For every action force there is an opposite and equal reaction force.

Question 20

What are the 2 equations involved in forces?

Answer 20

Force=mass÷acceleration

Weight=mass x gravitational field strenth

Question 21

What is the difference between weight and mass?

Answer 21

Weight is a force, mass is not.