Chapter 1 : Motion, Forces, and Energy

What unit is weight measured in?

Newtons ( N)

How to calculate the gravitational field strength, mass, and weight?

g = W/m

W = m * g

m = W / g

The gravitational field strength on earth

the gravitational field strength on earth is 9.8N/kg. So 1.0kg object is around 9.8N and an object with a mass of 100kg would have a weight of around 980N.

what is the difference between mass and weight?

Mass - typically measured in kg and is how much material is present

Weight - measured in newtons (N) and is the gravitational force on an object

Calculate the mass of someone who is 500N

500/9.8 =51.02kg

Calculate the weight of someone whose mass is 60kg

60 × 9.8 = 588N

is mass a scalar or vector quantity?

scalar

is weight a vector or scalar?

vector

is gravitational field strength vector or scalar?

vector

what is the gravitational field strength on the surface of the moon?

1.6kg

Why would your weight change even though your mass remains the same if you were on the moon?

Your mass does not change but your weight would because the gravitational field strength is 1/6 of that on the earth and so is the gravitational force.

what is the acceleration of free fall equivalent too?

gravitational field strength

N/kg = m/s²

calculate the weight of a 140g phone on the surface of the earth

140g = 0.14kg

0.14 × 9.8 = 1.372N

What are the units for gravitational field strength?

N/kg

what is the difference between a scalar and vector quantity

a scalar quantity only has a magnitude while a vector has both magnitude and direction

How do you calculate speed?

Speed = distance/time

v = s/t

how to calculate average speed?

average speed = total distance travelled / total time taken

calculate the speed of a car that travels 500m in 20s

v = s/t

v = 500/20

v= 25 m/s

A cyclist has an average speed of 5.0 m/s for 2.0 min. Calculate the total distance travelled?

s = v * t

s = 5.0 × 2.0 × 60

s = 600m

Velocity

speed in a given direction (vector)

explain why velocity can have a minus sign

it tells you that an object is traveling in the opposite direction. So a velocity of -280 m/s upwards is actually a velocity of 280 m/s downwards

Acceleration

change in velocity per unit time

what is this symbol ‘∆’?

the greek delta symbol which means ‘change in…’

how to calculate acceleration

a = ∆v / ∆t

∆v is the change in velocity

∆t is the change in time

what are the units for acceleration

m/s²

define density

how closely packed the particles are in a solid, liquid or gas

how to calculate the density

density = mass/volume

p = m/v

Why should your line of sight be perpendicular to the ruler?

When the ruler is nearer to the eye than the object being measured, the reading will change as the eye moves

meniscus

surface of most liquids bend up or down near the walls of the measuring cylinder

How long is the delay of reaction time?

0.2s

what is the density of water?

1.0g/cm³

what is force measured in?

Newtons (n)

How do you calculate resultant force?

force = mass x acceleration

what is a balanced force?

when there is no resultant force.

when there are at least 2 forces acting on an object and they are balanced, the object will be stationary or move at a constant speed

what is resultant force?

total of all forces added-up

how to find the density of an irregular object

measure the mass of the object on a balance. Pour enough water to submerge the object and record it as volume 1. Add the object into the water and record volume 2. Subtract volume 2 from 1 to find the volume of the object. Divide the mass by the volume to find the density.

what are the different scalar quantities?

distance, speed, time, mass, energy, temperature, volume