2 Motion & Energy

Question 1

How do you work out the speed/ velocity from a d-t graph?

Answer 1

Gradient of d-t graph

=speed/ velocity

Question 2

How do you work out the distance/ displacement from a v-t graph?

Answer 2

Area under graph

Question 3

How do you work out the acceleration from a v-t graph?

Answer 3

Gradient of v-t graph

= acceleration

Question 4

Formula for average speed

Answer 4

Average speed =

Total distance/ total time

Question 5

What is inertia & Newton’s 1st law?

Answer 5

When the resultant force is zero

Stationary objects remain at rest

Moving objects continue moving at a constant velocity

Question 6

State Newton’s 2nd law

Answer 6

A non-zero resultant force results in acceleration

F=ma

Question 7

State Newton’s 3rd law

Answer 7

When 2 objects interact, the forces exerted on each other are equal & opposite

Forces:
Same type of force
Equal in size
In opposite directions
Act in different objects

Question 8

What is momentum

Answer 8

Quantity of the motion of a moving, measured as a product of its MASS & VELOCITY

Question 9

Equation to calculate momentum

Answer 9

p = mv

p= Kg m/s

Question 10

State the law of momentum

Answer 10

Momentum is conserved!
When no external forces act

Moment before a collision is the same as the momentum after a collision

Question 11

How is a stopping distance calculated?

Answer 11

Thinking distance + Braking distance

Question 12

What happens to the stopping distance w extra speed?

State the equation that is used to calculate the
Kinetic Energy transferred

Answer 12

Extra speed&raquo_space; alarming increase in stopping distances

Ek transferred = Work done by Brakes
1/2 mv^2 = F x d
(Car Speed) = (max. braking force) x braking distance

Question 13

What happens during crashes

Referencing momentum & Ek

Answer 13

In a short time period:
A lot of Ek is converted into other forms of energy

Big changes in momentum
= huge forces experienced

Question 14

How do crumple zones improve safety during crashes?

Answer 14

Crumple zones increase the impact time and decrease the the force produced by the sudden change in momentum

Question 15

Name 3 safety designs in cars

Answer 15

Air bags
Slow you down more gradually and prevents you hitting hard surfaces

Seatbelts
Stretch slightly to increase the time taken to stop (impact time) and reduced the force acting on the chest
Some Ek of the wearer is also absorbed by the stretching seatbelt

Side impact bars
Ek is directed away from passengers to crumple zones
(Front and back if car which changes the shape of the car)

Question 16

How do brakes work to stop a car?

Traditional
Regenerative

Answer 16

Energy is transferred/ work is done when brakes are applied

Traditional
Ek&raquo_space; heat and sound energy
Which dissipates

Regenerative
Brakes put motor into reverse to slow the wheels down
Motor acts as an electrical generator
Ek&raquo_space; Electrical energy&raquo_space; Chemical energy

Chemical energy is stored instead of being wasted in traditional systems

Question 17

Name the 3 forms of stored energy

Definition of stored energy

Answer 17

GPE, Elastic Potential & Chemical energy

Stored energy is waiting to be converted into other forms of energy