IT ’S NOT THE
𝑣𝑓 =
∆𝑑
∆𝑡
T H AT G E T S Y O U , I T ’ S
THE
𝐹 = 𝑚
∆𝑣
∆𝑡
Forces
Objectives
1. Define force and the equation to back it up.
2. Draw and describe the forces acting on objects in certain situations.
3. Define Balanced and Unbalanced forces
4. Answer problems related to force.
What is a Force?
A force is a push or a pull on an object with mass that causes it to change
velocity (to accelerate).
𝐹𝑁𝑒𝑡 = 𝑚𝑎
Force is equal to the mass multiplied by the acceleration.
Force has the units of Newtons (N).
Questions
Calculate the force exerted when:
1. A 90 kg rugby player accelerates at 1.5 ms-2
2. An airbus A320 airplane has a mass of 80 000 kg. In order to stop in time, it
must decelerate on the runway at a rate of 3 ms-2. Calculate the force needed
for the plane to stop.
3. A 1000 kg car increases its speed from 0 to 28 ms-1 in 7 seconds. Calculate its
force.
Force Types
Two types of forces:
- Contact Forces, for example kicking/throwing a ball or pulling/pushing a cart.
- Non-Contact Forces (Field Forces), gravity or magnetic fields.
Normal Force/Support Force
Forces in Action
Gravity
(g)
Normal Force/Support Force
Forces in Action
Friction
Applied Force (Push)
Gravity
(g)
Normal Force/Support Force
Forces in Action
Friction
Applied Force (Push)
Gravity
(g)
100N
Net Force
The sum of the acting forces
on an object/thing.
100N
500N
100N
Objectives
1. Define mass and weight (yes they are different!)
2. Calculate weight force when exposed to different gravities
3. Understand and describe the relationship of area in pressure
4. Solve problems related to pressure
Weight
Weight is different from mass.
Mass is a measurement of the amount of matter something contains.
Weight is the measurement of the pull of gravity on an object.
𝐹𝑊 = mg
𝐹𝑊 is the weight force, m is the mass and g is gravity (−10m/s −2 on earth)
What is Pressure?
Pressure is the amount of force exerted over an area
𝑃=
𝐹
𝐴
A is the area in m2 , will most likely need to convert from cm to m
The smaller the area the force is exerted over, the greater the pressure applied
Pressure has units of Nm−2
Past Exam Questions
Past Exam Questions