Test: Newton’s First Law of Motion

Given, Fext = 0.

We know that F = ma 

(where F is force, m is mass and a is acceleration)

As Mass (m) cannot be zero, therefore a = 0. 

• We know, every action has an equal and opposite reaction from Newton’s third law of motion.
• In this case, when the bull pulls a cart by a force say F, the cart also pulls the bull with an equal force F in the opposite direction and the net force is zero.
• But the bull is also pushing the ground at an angle by a force say F1.
• Now the ground also pushes the bull with a force of the same magnitude F1 but in opposite direction.
• The vertical component of the force balances with the weight of the bull and the cart but the unbalanced horizontal component of the force (if greater than frictional force) makes the bull move forward.

• The Law of inertia also called Newton’s first law, postulates in physics 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 force.
• According to the law of inertia, a particle tends to remain at rest or in uniform motion unless acted by an external force.
• When you jerk the blanket, it moves, but the dust particles remain at their original position.
• And finally, the dust gets separated. When we beat the blanket with a stick, it comes into motion.
• But the dust particles continue to be at rest due to inertia and get detached from the blanket.

According to Newton’s First  Law, the cloth is set in motion but the chinaware continues to remain in its state of rest; hence it is not damaged.

Additional Information: Newton's first law of motion is often stated as: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Hence, option A is correct.

Force of inertia = ma

Let the masses be 1x and 5x

Force of inertia for 1st body= 1x * a

Force of inertia for 2nd = 5x * a

Ratio= x * a / 5x * a = 1:5

Additional Information: The inability of a body to change it’s state of rest or uniform motion is called inertia.

• It is usually seen that during rainy days we tend to slip because rainwater acts as a lubricant between our feet and the ground.  

• This lubrication (rainwater) converts dry friction into fluid friction. 

• That is, the friction between feet and ground reduces, making us slip.

Therefore, due to less friction, we slip on a rainy day.

F = F1 + F2 + F3 = ( 20i + 30j) N+(8i - 50j) N+(2i +2 j) N

=(20+8+2)i+(30-50+2)j

F=30i - 18j

F = ma

Substituting F and m = 6 kg (given) in the above equation we get,

30i - 18j = 6*a

A = 5i - 3j

Hence (b) is correct choice

When the bus moves, the passenger's body comes into a state of motion but when the bus stops the lower part of the body which is in contact with the floor comes into a state of rest whereas the upper part of the body still remains in the state of motion and because of this the upper part of the body falls in the forward direction. This is due to the presence of inertia. 

Hence the correct answer is C.

Given: 
Speed of the particle after a time 2T, 




 

• Newton’s first law of inertia states that an object at rest or in motion tends to stay at rest or moving with constant motion unless enacted upon by an unbalanced force. 

• The law of inertia relates to the sport of cycling due to the fact that the cyclist is in constant motion when on the cycle. 

• The motion of the bike is caused by the rider pressing down upon the pedals, which, in turn, enables the rider to accelerate on the bike. 

• As well, the cyclist will continue to move unless enacted upon by an opposing unbalanced force, such as the force of friction on the bike tires, when the bike decelerates to a stop. 

• The Law of Inertia is also displayed when the cyclist begins to move on the bicycle from a stop. 

• The action is related to the concept of Inertia for the reason that the cyclist is applying an unbalanced force to the bicycle pedals when not in motion. As a result, the bicycle would gain acceleration and therefore begin to move.

Therefore the correct answer is B.