The article discusses about various methods on how to find net force with mass and speed and its solved problems.
We assume a speed instead of velocity when we only discuss how much distance an object traveled in unit time instead of about which direction it traveled when a net force acts. It facilitates us to discover the net force with mass and speed or constant speed using Newton’s Laws and force formulas.
Read more about How to Calculate Speed from Force and Mass.
How to Find Net Force with Mass and Speed using Newton’s Law Motion?
Newton’s second law of motion assists us in finding the net force with mass and speed.
An object with mass at rest drives speed to a certain distance when a net force acts. To find the net force with mass and speed using Newton’s second law, we first must convert an object’s velocity, expressed in Kilometre/hour, into its speed as meter/second.
Note that velocity is denoted as ‘v’ and speed is denoted as ‘v’ (italic v)
The Newton second law expresses,
Fnet = ma
Fnet ==m*[(v-v0)/(t-t0)
Suppose an object begins moving from rest. t0 = 0 and v0 = 0.
Fnet =m*(v/t)
The velocity is expressed in Km/hr.
1km = 1000km
1hr = 3600 sec
So when we defined velocity v into speed v,
v=v(1000/3600)m/sec
Read more about How to Find Net Force with Mass and Velocity.
When a batter hits the ball with a mass of 5kg, its velocity changes from 10km/hr to 15km/hr in unit time from 5sec to 10sec. Calculate the net force on the ball in terms of its mass and speed.
Given:
m = 5kg
v0 = 10km/hr
v = 15km/hr
t0 = 5sec
t = 10sec
To Find:
- v =?
- Fnet =?
Formula:
Fnet ==m*[(v-v0)/(t-t0)]
Solution:
We need to calculate speed from velocity before calculating the net force.
Let’s calculate the net force on the ball using Newton’s second law of motion.
The net force on a ball with mass and speed is 1.46N.
How to Find Net Force with Mass and Constant Speed?
The net force with mass and constant speed is calculated from vertical forces only.
When no net force acts, an object travels with constant speed linearly, and its velocity becomes constant as it proceeds in a linear direction. Since a pair of horizontal forces balance each other, the speed becomes constant, and the pair of vertical forces deliver the net force with mass and constant speed.
Out of four forces that act in all directions, the horizontal forces, such as applied force and friction force, balanced each other when the speed was constant. Only vertical forces, such as normal force or gravity, can accelerate an object proceeding with constant speed. But both vertical forces have the exact formula. i.e., mg. Therefore, the net force with mass and constant speed is estimated when normal, and gravity forces cannot cancel each other.
Read more about Types of Forces.
The box has a mass of 6 kg and moves with a constant speed of 5 m/sec when pulled by the force of 50N at 30°. Calculate the values of different forces and net force acts on the box with its mass and constant speed. (g = 9.8m/s2)
Given:
m = 6kg
v = 5m/sec
Fi = 50N
θ = 30°
To Find:
- Fg =?
- Fy =?
- Fx =?
- FN =?
- Ff = ?
- Fnet =?
Formula:
- Fg= mg
- Fy = Fisinθ
- Fx = Ficosθ
- FN + Fy = Fg
- Fnet = Fhoz + Fvert
Solution:
Let’s find each force acting on the box before calculating net force.
The gravity force formula is,
Fg = mg
Fg = 6 x 9.8
Fg = 58.8
The gravity force is 58.8N.
Since force is applied at an angle, it is resolved into two components, Fx and Fy.
The vertical component Fyperpendicular to the box is calculated using the trigonometric function.
Fy = Fisinθ
Fy = 50 x sin (30°)
Fy = 25
The vertical component of applied force is 25N.
The horizontal component Fx parallel to the box is calculated using the trigonometric function.
Fx = Ficosθ
Fx = 50 x cos (30°)
Fx = 43.3N
The horizontal component of applied force is 43.3N.
The normal force perpendicular to the box and along the vertical component of applied force Fy is calculated as,
FN + Fy = Fg
FN = Fg – Fy
FN = 58.8 – 25
FN = 33.8
The normal force is 33.8N.
Since the box is moving with a constant speed of 5m/sec, the horizontal forces such as the horizontal component of applied force and friction force must balance each other.
That means the friction force Ff = 43.3N.
The net force on the box is calculated by adding only vertical forces.
Fnet = Fvert
Fnet = FN + (-Fg)
Fnet = 33.8 – 58.8
Fnet = – 22
The net force acts on the box with its mass and the constant speed is -22N.
Read more about How to Find Net Force?
How to Find Net Force with Mass and Constant Speed in Circular Motion?
The net force with mass and constant speed in circular motion is the centripetal force only.
When there is no force on an object proceeding circularly, its magnitude of velocity, i.e., speed, is constant, but its direction constantly changes. So an object with constant speed is accelerating in a circular path, and the net force that is liable for circular motion is the centripetal force.
Newton’s laws display that a net force is mandated to accelerate an object. An object rolls with constant speed accelerated towards the center during circular motion even with no net force – including vertical and horizontal forces. The only net force that acts on an object in a circular motion when it moves with constant speed is the centripetal force.
(credit: shutterstock)
As Newton’s second law, Fnet = ma.
The centripetal force that causes the acceleration to an object which undergoes uniform circular motion is v2/R.
The net force due to centripetal force is,
Fnet =m*(v2/R)
Read more about Angular Motion
A motorcyclist has a mass of 50kg riding in a vertical circle with a constant speed of 10 m/sec in a hollow sphere of 20 m. Calculate the net force act on motorcyclist with its mass and constant speed.
Given:
m = 50kg
v = 10m/sec
R = 20m
To Find: Fnet=?
Formula:
Fnet =m*(v2/R)
Solution:
The net force on motorcyclists is calculated using the centripetal force formula.
Fnet =m*(v2/R)
Substituting all values,
Fnet =50*(102/20)
Fnet =5000/20
Fnet = 250
The net force on a motorcyclist with constant speed is 250N.
Read more about Net Force Vs Force.
