LAWS OF MOTION
Very Short Question Answers
Q1. What is inertia? What gives the measure of inertia?
Ans. Inertia: The inability of a body to change its state by itself is known as inertia. Mass is the measure of inertia.
Q2. According to Newton’s third law, every force is accompanied by an equal and opposite force. How can a movement ever take place?
Ans. According to newton’s third law of motion action and reaction act on two different bodies. Hence motion is possible
Q3. When a bullet is fired from a gun, the gun gives a kick in the backward direction.Explain?
Ans. According to the law of conservation of linear momentum.
$m_{1}u_{1}+m_{2}u_{2}=m_{1}v_{1}+m_{2}v_{2}$
$0=m_{1}v_{1}+m_{2}v_{2}$
$ m_{1}v_{1}=\,-\,m_{2}v_{2}$
minus sign indicates gun and bullet move in opposite direction after fired. Hence, gun will
kick backwards.
Q4. Why does a heavy rifle not recoil as strongly as a light rifle using the same cartridges?
Ans. According to law of conservation of linear momentum
Hence heavy rifle recoil less as compare to light rifle.
Q5. If a bomb at rest explodes into two pieces, the pieces must travel in opposite directions. Explain?
Ans. According to the law of conservation of linear momentum.
$m_{1}u_{1}+m_{2}u_{2}=m_{1}v_{1}+m_{2}v_{2}$
$0=m_{1}v_{1}+m_{2}v_{2}$
$ m_{1}v_{1}=\,-\,m_{2}v_{2}$
minus sign indicates two pieces move in opposite direction after explosion.
Q6. Define force. What are the basic forces in nature?
Ans. Force: The physical quantity that changes or tries to change the state of rest or of uniform
motion along a straight line is called force.
The basic forces in nature are :
- Gravitational force
- Electromagnetic force
- Strong nuclear force
- Weak nuclear force.
Q7. Can the coefficient of friction be greater than one?
Ans. Yes. The coefficient of friction is greater than one.
Q8. Why does the car with flattened tyre stop sooner than the one with inflated tyres?
Ans. A flattened tyre has got more surface area of contact due to deformation than an inflated tyre. Hence friction is more in the case of a flattened tyre.
Q9. A horse has to pull harder during the start of the motion than later. Explain?
Ans. Static friction is more than kinetic friction. To overcome static friction initially horse
should apply more force than later.
Q10. What happen to the coefficient of friction, if the weight of the body is doubled?
Ans. Coefficient of friction (𝜇) is independent of mass of the body. Therefore, coefficient of
friction does not change.