Force And Laws Of Motion

The momentum is given by , p = m×v , that is product of mass and velocity. As we know that mass of both the objects will be constant and what will change is velocity , so car due to heavier mass and hence more inertia of motion will remain in motion and will experience little reduction in speed whereas bird has negligible mass as compared to car , so it will experience more drastic change in it’s velocity and in momentum.

A bowler runs because it wants to give speed to the bowling ball and hence momentum , so that the bowler just leaves the ball when he reaches the line and the ball keeps on moving due to the momentum provided by running of bowler.

Due to the inertia of rest of the book and impulsive force applied by us we are able to jerk the paper out from under the book without moving the book.

When we kick a football due to it’s light weight it moves and gives less recoil to us due to law of conservation momentum and when we kick a heavy stone it gives us more recoil to conserve momentum and has more inertia of rest , so we get hurt by kicking a stone.

Statement of Newton’s third law of motion is “To every action there is always an equal and opposite reaction.”

Force is generally described as a push or a pull but it is also told as a product of mass and acceleration or rate of change in momentum.

1. Force can change the direction of motion of the object.

2. Force can change the speed of moving of object.

Grinding stone is like a wheel and at every point of the wheel at the periphery, the direction of linear velocity is tangential due to the inertia of motion, so that is why the sparks go tangential.

The first law states that when a body in motion stays in motion and a body at rest stays at rest until an external force is applied. But in the case of rolling of the ball, the ball stops after some time because frictional force is acting on the ball every time which keeps on reducing its speed.

Given:

Mas of bullet = 10g

Velocity of bullet = 150ms^-1

Mass of pistol = 2 kg

Due to the law of conservation of momentum the momentum of the bullet is equal to the recoil of the gun. So the sum of the momentum of both the objects is equal to zero.

M_bV_b = –M_gV_g , Now ,

This is an inherent property called inertia of rest which is directly proportional to the mass of the object.

Examples: –

1. When we beat carpet dust particles comes out.

2. When you shake the branch of tree fruits or leaves comes out.

Slope in the velocity versus time graph is acceleration and hence it is due to application of force.

a) . The slope is constant, so the force is constant and is acting in the direction of motion.

b) . The force acting on the object is zero because there is no velocity change.

c) . The slope is constant, so the force is constant and is acting opposite to the direction of motion.

Reasons:–

a) . This is due to the inertia of motion which is that the body in motion likes to stay in motion and resist and change in its state.

b) This is due to the Newtons third law of motion.

As the man is trying to push himself forward, he is simultaneously pushing the boat back.

(a)

a) Choose a heavy object like a table or a box, which you can move only by pushing hard.

b) Try to push it all by yourself. Can you move it?

c) Now ask one of your friends to help you in pushing it in the same direction.

d) Is it easier to move it now? Can you explain why? Next, push the same object, but ask your friend to push it from the opposite side.

e) Does the object move? If it does, note the direction in which it moves. Can you guess which one of you is applying a larger force?

(b)
i. The forces acting on the suitcase are unbalanced.

The air friction, weight & the airspeed are acting on the ball. Example, the figure is given below:

ii. Balanced forces.

iii. There are balanced forces.

According to the law of conservation of momentum

When two or more bodies act upon each other their total momentum remains constant provided no external forces are acting

•So, Momentum is never created or destroyed.

•When this law is applied for a collision between two bodies, the total momentum of the colliding bodies before the collision is equal to the total momentum after the collision.

•We can apply this law for a collision between two vehicles. This law is applicable for all types of collisions.

•Consider two particles say A and B of mass m1 and m2 collide with each other and forces acting on these particles are only the ones they exert on each other.

•Let u₁ and v₁ be the initial and final velocities of particle A and similarly, u₂ and v₂for particle B. Let the two particles be in contact for a time t.

So, Change in momentum of A=m₁ (v₁-u₁) Change in the momentum of B=m₂ (v₂-u₂ )

•During the collision, let A impart an average force equal to F_BA on B and let B exert an average F_ABon A. We know that from third law of motion F_BA=F_AB eq.(4)
Here,

canceling t on both sides and rearranging the equation we get
m₁u₁+m₂u₂ = m₁v₁+m₂v₂ eq.(5)
Now, m₁u₁+m₂u₂ represents the total momentum of particles A and B before collision and m₁v₁+m₂v₂ represents the total momentum of particles after the collision. This means that
Total momentum before collision=total momentum after the collision

•Equation 5 which m₁u₁+m₂u₂ = m₁v₁+m₂v₂ ,is known as the law of conservation of momentum.

(a) We observe that sonam is very curious in understanding natural phenomenons about the gravitational forces between sun and moon

(b) The characterstic value of her teacher is as below:

• expert communication skills
• superior listening skills
• deep knowledge and passion for their subject matter
• the ability to build caring relationships with students
• friendliness and approachability
• excellent preparation and organization skills
• strong work ethic
• community-building skills
• high expectations for all

(c). Balanced forces are those in which F_net = 0 N, whereas Unbalanced forces are those in which F_net ≠ 0 N.

(d). Gravitational force is a weak force and it depends upon distance and earth is closer to us than sun or moon, so pulling of the earth is more effective than the other two.

(e) Good reading habits led to constructive learning. The good heading habits like reading newspaper, science journal led a constructive learning of the new technology and ideas in his dictionary which led him to question existing theory which led to constructive learning