#4
Motion & Force
Name:_________KEY____________________
Science 8
Law 2 app problems
Date:________________
Hr:_____
Ch. 4 The Laws of Motion
1. a 85-kg mass has an acceleration of 5.5 m/s/s. What is the net force applied?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
m= 85 kg
a = 5.5
m/s/s
Force?
F=mxa
F = 85 kg x 5.5 m/s/s
F= 467.5 N
2. A 3200-N force is applied to a 160-kg mass. What is the acceleration of the mass?
Info given
F=3200 N
What are you
asked to find?
Acceleration?
Formula
a = F/m
Substitute and solve (show
work with units)
a= 3200 N / 160 kg
Answer that
includes
units
a= 20 m/s/s
M=160 kg
3. If you are pushing a box with a force of 20 N and there is a force of 7N on the box due to sliding
friction, what is the net force on the box? Draw a picture and label.
Push Force
20N
Sliding Friction
7N
Fnet = 20N – 7N = 13N to the right
4. If you are pushing a box with a force of 85 N and there is a force of 92N on the box due to sliding
friction, what is the net force on the box? Draw a picture and label.
Push Force
85 N
Sliding Friction
92 N
Fnet = 85N – 92N = -7N The box does
NOT move.
5. What is the net force on a 4000-kg car that doubles its speed from 15 m/s to 30 m/s over 10
seconds? (Hint: You must calculate acceleration first, then find the force)
Info given
What are you
asked to find?
M = 4000kg
Formula
a=vf-vi/t
Vi=15 m/s
Vf=30 m/s
Force?
F=mxa
Substitute and solve (show
work with units)
a= (30 m/s – 15 m/s) / 10 s
a = 15 m/s / 10 s
a = 1.5 m/s/s
Answer that
includes
units
F=6000 N
F=4000 kg x 1.5 m/s/s
T=10 sec
6. A book with a mass of 1-kg is sliding on a table. If the frictional force on the book is 5N, calculate
the book’s acceleration. Is it speeding up or slowing down?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
a = 5 m/s/s
m = 1 kg
F=5N
Acceleration?
Speeding up or
slowing down?
a = f/m
a = 5 N / 1 kg
Slowing
down as it
moves
across the
table
7. How much force is needed to accelerate a 3,500,000–g car at a rate of 3 m/s/s?
Info given
What are you
asked to find?
Formula
m=3,500,000g
m = 3500 kg
a = 3 m/s/s
Substitute and solve (show
work with units)
F = 3500 kg x 3 m/s/s
Force?
Answer that
includes
units
F=10,500 N
F=mxa
8. If a 70,000-g swimmer pushes off a pool wall with a force of 250 N, at what rate will the swimmer
accelerate from the wall?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
m=70,000g
m=70 kg
Acceleration?
F=250 N
a=F/m
a= 250 N/70 kg
A = 3.57
m/s/s
Motion & Force
Science 8
Law 2 app problems
Ch. 4 The Laws of Motion
#4
Name:______________________________
Date:________________
Hr:_____
1. a 85-kg mass has an acceleration of 5.5 m/s/s. What is the net force applied?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
2. A 3200-N force is applied to a 160-kg mass. What is the acceleration of the mass?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
3. If you are pushing a box with a force of 20 N and there is a force of 7N on the box due to sliding
friction, what is the net force on the box? Draw a picture and label.
4. If you are pushing a box with a force of 85 N and there is a force of 92N on the box due to sliding
friction, what is the net force on the box? Draw a picture and label.
5. What is the net force on a 4000-kg car that doubles its speed from 15 m/s to 30 m/s over 10
seconds? (Hint: You must calculate acceleration first, then find the force)
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
6. A book with a mass of 1-kg is sliding on a table. If the frictional force on the book is 5N, calculate
the book’s acceleration. Is it speeding up or slowing down?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
7. How much force is needed to accelerate a 3,500,000–g car at a rate of 3 m/s/s?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units
8. If a 70,000-g swimmer pushes off a pool wall with a force of 250 N, at what rate will the swimmer
accelerate from the wall?
Info given
What are you
asked to find?
Formula
Substitute and solve (show
work with units)
Answer that
includes
units