Download forces review activity

Happy Monday!
1. Grab your calculator
2. Get ready for warm up #5
3. Turn in your “One Pager”
assignment
4. Test review is worth a grade
Test tomorrow!!
Warm up # 5
Assume a 15 kg object is moving at the
acceleration in the graph above. What force is
required to make the object move at the
acceleration in the graph?
Forces and Newton’s Laws Formulas
F= ma
F f = m FN
Quick review
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•
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NET force, or FNET = total amount of force
if two forces are in the same direction, add
If they are pulling in opposite direction, subtract
Types of forces: FWEIGHT FTENSION, FPUSH, FPULL,
FNORMAL, FFRICTION, FTHRUST
• You only have 2 equations:
1. F= ma
2. Ff = m (m)(g)
Name those units!
What are the units for force?
Newtons
What are the units for mass?
Kilograms
What are the units for weight?
Newtons
What are the units for acceleration?
m/s2
What are the units for velocity?
m/s
What is the SYMBOL for the coefficient of friction?
m
. Identify each of the following as: FWEIGHT
FTENSION, FPUSH, FPULL, FNORMAL, FFRICTION
Placing a heavy object on a table
FWEIGHT
The table pushes back against the object
FNORMAL
Bicycle brakes
FFRICTION
Playing tug of war
FTENSION
Your friend shoves you
FPUSH
Check Your Understanding
1. What acceleration will result when a 12 N net
force applied to a 3 kg object?
4 m/s2
2. A net force of 16 N causes2 a mass to
accelerate at a rate of 5 m/s . Determine the
mass.
3.2 kg
3. How much force is needed to accelerate a 66
kg skier 1 m/sec/sec?
66 N
7
Which has more inertia?
Bicycle or car?
Basketball or golfball?
INERTIA = MASS
WEIGHT AND THE NORMAL FORCE
• Weight is defined as mass being accelerated
towards the Earth by gravity (9.8 m/s2)
• What is the formula for determining the
weight of something?
• FWEIGHT = m (9.8)
• What is the NORMAL FORCE, or FNORMAL ,
almost always equal to?
• WEIGHT FORCE, or FWEIGHT
WEIGHT AND THE NORMAL FORCE
What is FWEIGHT ?
What is FNORMAL?
118 N
12 kg
118 N
Check your understanding
Jennifer has a mass of 48 kg. What is her weight in
Newtons?
470 N
A book that has a weight of 42 N is resting on the
table. What is the normal force? (FNORMAL or FN)
42N
Calculate the normal force!
157 N
FWEIGHT = 6 x 9.8 = 58.8 N
+ 10.0N
69 N
What is the NET force?
5 N to the left
0N
What is the Normal force equal to?
FWEIGHT
Calculate Acceleration
10m/s2
0.27 m/s2
Calculate the following
What is the magnitude of the friction force if a
sled has a mass of 78 kg coefficient of friction
is 0.15?
115 N
Find the friction force if a boy on ice skates has a
mass of 80 kg and the coefficient of friction is
.08.
63 N
Calculate the following:
A huge pile of leaves was wrapped in a tarp in
the middle of a lawn. The wrapped leaves
weigh 880 N. The coefficient of friction for the
lawn is 0.55. Find friction force.
Remember: Ff = m(FN)
484 N
A car got stuck in the mud. Two boys attached ropes and tried to
pull the 3000 kilogram car out. One boy pulls to the left with a
force of 250 N and the other boy pulls in the same direction
with a force of 280 N.
Draw a free body diagram of scenario above.
The coefficient of friction is 0.60.
Calculate the forces acting upon the car
29,400N
530N
1800N
What is the NET force
acting upon the car?
29,400N
1270N to the right
Will the boys be able to pull the car out? No, they must exert more force