Force, Motion & Energy

Question 1

What is the difference between distance and displacement?

Answer 1

Distance is the amount of ground traveled whereas displacement is from the starting point to the the finishing point.

Question 2

What is the different between a vector and a scalar?

Answer 2

Scalar describes a movement by magnitude however a vector describes a movement by magnitude AND direction.

Question 3

What is the difference between speed and velocity?

Answer 3

Speed is distance/time and is the rate on change in position. Velocity is displacement/time therefore it has direction. s = 3m, v = 3m West

Question 4

What is the difference between average speed and instantaneous speed?

Answer 4

Average speed is the average rate of change over a period of time. However instantaneous speed is the speed at an exact given moment.

Question 5

How do you convert km/h to m/s?

Answer 5

km/h — ÷ 3.6 — m/s (x 3.6 opposite way)

Question 6

How do you find an objects acceleration?

Answer 6

a = (v-u)/t
a = (velocity - initial velocity)/time

Question 7

How do you find velocity, acceleration or distance on a motion graph?

Answer 7

s/t graph = gradient is velocity, area is distance
v/t graph = gradient is acceleration, area is displacement
a/t graph = area is change in velocity

Question 8

Define equilibrium.

Answer 8

the forces are equal on an object (no net force) therefore there is no change in behaviour.

Question 9

Explain normal, friction, kinetic and static force.

Answer 9

Normal = perpendicular to the surface the object is in contact with (equal and opposite)
Friction = force between to objects in contact
Kinetic = friction due to motion
Static = friction between stationary objects

Question 10

What is the different between a FBD and a System diagram?

Answer 10

FBD = a simple diagram with a 2D object and the forces acting upon it
SD = Sketch all objects in the situation in more detail

Question 11

1st Law Explain the Law of Inertia.

Answer 11

If the net force acting on an object is zero, that object will maintain its state of rest or constant velocity. It will only change if an unbalanced force acts upon it.

Question 12

2nd Law Explain F = ma

Answer 12

The acceleration is directly proportional to the net force and mass.
Force (N) = mass (kg) x acceleration (m/s2)

Question 13

3rd Law Explain Newtons final law (equal + opposite)

Answer 13

For every action force their is a simultaneous reaction force equal in magnitude but opposite in direction.

Question 14

How do you find an objects gravitational potential energy?

Answer 14

ΔEg=mgh

mass x gravity x height

Question 15

How do you find an objects kinetic energy?

Answer 15

Ek= 1/2 mv^2
half x mass x velocity(squared)
ΔEk= 1/2 mv^2 - 1/2 mu^2

Question 16

Define work (+ equation)

Answer 16

work is energy transferred to an object when a force moves it a distance (joules)
work = fs (force x displacement)
work = fscos(theta)
work = ΔE

Question 17

When will the work being done on an object be zero?

Answer 17

displacement or force = zero

If ‘f’ is perpendicular to ‘d’

Question 18

Why is an energy transfer never 100% efficient?

Answer 18

Some of the energy can be transferred into a place it doesn’t want to go.

Question 19

How do you calculate efficiency?

Answer 19

%efficiency = (energy out/ energy in) x 100
%efficiency = (height 2/ height 1) x 100

Question 20

What is the formula for power?

Answer 20

P = ΔE/Δt
P = W/Δt

Question 21

What is the difference between momentum and impulse?

Answer 21

momentum is the product of an objects mass and velocity
- p = mv
impulse is the change in momentum
- I = Δp = mv - mu

Question 22

What is the difference between elastic and inelastic collisions?

Answer 22

An elastic collision has no loss of kinetic energy whereas and inelastic collision will have a portion of energy loss