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2. “The unbalanced force acting on an object equals the
object’s mass times its acceleration”.
a =
𝐹𝑛𝑒𝑡 𝑓𝑜𝑟𝑐𝑒
𝑚𝑎𝑠𝑠
m =
𝐹𝑛𝑒𝑡 𝑓𝑜𝑟𝑐𝑒
𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛

3. The law of acceleration defined as,
a =
𝐹𝑛𝑒𝑡
𝑚
where a represents acceleration, m is mass, and Fnet is the
unbalanced force.
Therefore, 1 newton = 1 kg
𝑚
𝑠2 and 1 kg = 9.81 N (10N)
The pound (lb) is sometimes used as a unit of force. One
newton is equivalent to 0.225 lb. Conversely, 1 lb = 4.448 N.

4. Problem 1. You kick a 0.5 kg football with a force of 5 N.
What is the ball’s acceleration?
Given: Solution:
m = 0.5 kg
Fnet = 5 N
a =?
a =
𝐹𝑛𝑒𝑡
𝑚
=
5 𝑁
0.5 𝑘𝑔
= 10
𝑁
𝑘𝑔
=
10 𝑘𝑔 𝑚
𝑘𝑔 𝑠2
= 10
𝒎
𝒔𝟐
The acceleration of the football is
10 m/s2.

5. Problem 2. If a force of 15 N is applied on a 12 kg object, what
is the acceleration?
Given: Solution:
m = 12 kg
Fnet = 15 N
a =?
a =
𝐹𝑛𝑒𝑡
𝑚
=
15 𝑁
12 𝑘𝑔
= 1.25
𝑁
𝑘𝑔
=
1.25 𝑘𝑔 𝑚
𝑘𝑔 𝑠2
= 1.25
𝒎
𝐬𝟐
The acceleration of an object is
1.25 m/s2.

6. Problem 3. A 15 kg object was hit by a force of 20 N. What is
the acceleration?
Given: Solution:
m = 15 kg
Fnet = 20 N
a =?
a =
𝐹𝑛𝑒𝑡
𝑚
=
20𝑁
15𝑘𝑔
= 1.33
1𝑘𝑔 𝑚
𝑘𝑔𝑠2
= 1.33
𝒎
𝒔𝟐
The acceleration of an object is 1.33
𝑚
𝑠2 .

7. Problem 4. An elevator was used to lift three persons to the 14th
floor. If the elevator has a lifting force of 4,500 N and each
person weighs 100 kg, how much will the elevator accelerate
upward? Neglect the mass of the elevator. Assume 1 kg is
equivalent to 10 N.
Given:
mperson = 100kg mperson = wkg per person
wperson = (100 x 10) = 1,000 N wN = weight in Newton per person
(since 1 kg = 9.81 N or approximately 10 N)
Felev = 4,500N
Total of a person = 3 x(1,ooo N) = 3,000

8. Solution:
First, compute the total weight of the passengers is downward and the pull
of the elevator is upward, that is, you get the net force as:
Fnet = Felev – wtotal = 4,500 N – 3,000 N (3person x 1, 000) = 1,500 N
Then using Newton’s second law, you have:
a =
𝐹𝑛𝑒𝑡
𝑚
=
1,500 𝑁
300 𝑘𝑔
= 5 m/s2
The elevator will accelerate at 5 m/2.

9. Problem 5. If a force of 8 N to the left and a force of 30 N to the
right act on a 10-kg object, what is the net force? What is the
acceleration?
Given Solution
m = 10 kg
F = 8 N to the left
= 30 N to the right
a =?
Fnet =?
Fnet = 30 N – 8 N = 22 N
a =
𝐹𝑛𝑒𝑡
𝑚
=
22 𝑁
10𝑘𝑔
= 2.2
𝑘𝑔 𝑚
𝑘𝑔𝑠2 = 2.2 m/s2
The net force is 22 N and the
acceleration of the object is 2.2 m/s2.

10. Problem 6. If you kick a ball that weighs 0.8 kg, how much force
should be applied on it in order to have an acceleration of 15 m/s2?
Given Solution
m = 0.8 kg
a = 15 m/s2
Fnet = ?
Since F = ma, we have:
F = ma
= 0.8 kg x (15
𝑚
𝑠2) = 12 kg
𝑚
𝑠2
1 newton = 1 kg
𝑚
𝑠2
Therefore, the force should be applied
on the ball is 12 N.