Solved problems in Newton’s laws of motion – Normal force
1. An object resting on a table, shown in the figure below. Mass of the object is 1 kg. Accelerazione di gravità hè 9.8 m/s2. Determine the normal force exerted on the object by the table.
Cunnisciutu:
Massa (m) = 1 kg
Accelerazione di gravità (g) = 9.8 m/s2
Pesu (w) = mg = (1 kg)(9.8 m/s2) = 9.8 kg m/s2 = 9.8 Newtoni
Vulutu: normal force (N)
Soluzione:
The object is at rest on the table, so the net force on the object is zero (Newton’s first or second law). The weight of the object acts vertically downward, toward the center of the Earth. There must be another force on the object to balance the forza gravitazziunale. Object resting on the table, so that the table exerts this upward force. The force exerted by the table is often called a normal force (N). Normal means perpendicular.
Choose the upward direction as the positive y-direction. The net force on the object is :
∑Fy = 0
N – w = 0
N = w
N = m g
N = 9.8 Newton
The normal force on the object, exerted by the table is 9.8 N upward.
2. Two objects resting on a table. Missa of object 1 (m1) = 1 kg, mass of object 2 (m2) = 2 kg, acceleration due to gravity (g) =9.8 m/s2. Determine the magnitude and direction of the normal force exerted by m2 on the m1 and the normal force exerted by the table on the m2.
Vergogna à tè
Cunnisciutu:
Massa di l'ughjettu 1 (m1) = 1 kg
Massa di l'ughjettu 2 (m2) = 2 kg
Accelerazione di gravità (g) = 9.8 m/s2
Peso of object 1 (w1) = m1 g = (1)(9.8 m/s2) = 9.8 kg m/s2 = 9.8 Newtoni
Weight of object 2 (w2) = m2 g = (2)(9.8 m/s2) = 19.6 kg m/s2 = 19.6 Newtoni
Cercatu: N1 è N2
Soluzione:
(a) Normal force exerted by m2 to the m1 (N1)
N1 = w1 = 9.8 Newtoni
Direction of N1 is upward.
(b) Normal force exerted by the table on the m2 (N2)
N2 = w1 + w2 = 9.8 Newton + 19.6 Newton = 29.4 Newton
Direction of N2 is upward.
3. An object resting on the table. Mass of the object is 2 kg, acceleration due to gravity is 9.8 m/s2. Magnitude of the force F is 10 Newton. Find the magnitude and direction of the normal force exerted by the table on the object.
Vergogna à tè
Cunnisciutu:
Mass of the object (m) = 2 kg
Accelerazione di gravità (g) = 9.8 m/s2
Pesu (w) = mg = (2 kg)(9.8 m/s2) = 19.6 kg m/s2 = 19.6 Newtoni
Force F (F) = 10 Newton
Wanted : magnitude and direction of the normal force (N)
Soluzione:
direction of the normal force is upward.
Magnitude of the normal force :
∑F = 0
N – F – w = 0
N = F + w
N = 10 Newton + 20 Newton
N = 30 Newton
4. An object resting on a table. Object’s mass is 1 kg, acceleration due to gravity is 9,8 m/s2, force F1 is 10 N and force F2 is 20 N. Determine magnitude and direction of the normal force exerted by the table on the object. g = 9.8 m/s2
Vergogna à tè
Cunnisciutu:
Massa (m) = 1 kg
Accelerazione di gravità (g) = 9.8 m/s2
Pesu (w) = mg = (1 kg)(9.8 m/s2) = 9.8 kg m/s2 = 9.8 Newtoni
F1 = 10 Newtoni
F2 = 20 Newtoni
Cercatu: magnitude and direction of the normal force (N)
Soluzione:
Direction of the normal force is upward.
Magnitude of the normal force :
∑F = 0
N-F2 – w + F1 = 0
N = F2 + w – F1
N = 20 Newton + 9.8 Newton – 10 Newton
N = 19.8 Newton
5. Object’s mass (m) = 2 kg, acceleration of gravity (g) = 9.8 m/s2, angle = 30o. Find magnitude and direction of the normal force exerted on the object.
Soluzione:
w is weight, wx is horizontal component of the weight, wy is a vertical component of the weight, N is the normal force.
Cunnisciutu:
massa (m) = 2 kg
acceleration of gravity (g) = 9.8 m/s2
pesu (w) = mg = (2 kg)(9.8 m/s2) = 19.6 kg m/s2 = 19.6 Newtoni
wx = w sin 60o = (19.6 N)(0.5)√3= 9.8√3 Newton
wy = w cos 60 = (19.6 N)(0.5) = 9.8 Newton
Vulutu: forza normale (N)
Soluzione:
∑F = 0
N – oy = 0
N = wy
N = 9.8 Newton
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