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Answers
6)Newton's second law, which states that the force F acting on a body is equal to the mass m of the body multiplied by the acceleration a of its centre of mass, F = ma, is the basic equation of motion in classical mechanics.
7)Newton's first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.
8) We know that,
momentum =mass × velocity
here, mass=200g
200/1000kg=0.2kg
velocity = 15m/s
momentum =0.2×15
momentum=3 kg m/s
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10) Balanced forces :will cause no change in the speed of an object.
- Balanced forces acting on an object in opposite directions and equal in strength, as shown in the arrows below, do not cause a change in the speed of a moving object.
- Objects that are not moving will not start moving if acted on by balanced forces.
For example, in arm wrestling where there is no winner, the force exerted by each person is equal, but they are pushing in opposite directions.
- The resulting force (net force) is zero
Or, in a tug of war, if there is no movement in the rope, the two teams are exerting equal, but opposite forces that are balanced. Again, the resulting force (net force) is zero.
Unbalanced forces :
are not equal, and they always cause the motion of an object to change the speed and/or direction that it is moving.
- When two unbalanced forces are exerted in opposite directions, their combined force is equal to the difference between the two forces.
- The magnitude and direction of the net force affects the resulting motion
- This combined force is exerted in the direction of the larger force
For example, if two students push on opposite sides of a box sitting on the floor, the student on the left pushes with less force (small arrow) on the box than the student on the right side of the box (long arrow).
- The resulting action (net force: smaller arrow to the right of the = shows that the box will change its motion in the direction of the greater force.
11)Law of conservation of momentum states that total momentum of system remains conserved in the absence of external force.
Proof:
Consider a body of mass m1 moving with velocity U1, striking against another body of mass m2 moving with velocity U2.
Let the two bodies remain in contact with each other for a small interval "delta t".
Let F12 be the average force exerted by mass m1 on m2, and let F21 be the force on m2 due to m1.
Let v1 and v2 be the velcoities of two bodies after collision.
Momentum of mass m1 before collision=m1u1
Momentum of mass m2 after collision=m2u2
Momentum of mass m1 after collision=m1v1
By using the definition of impulse, change in momentum of mass m1