*Worksheet solutions for chapter: Force and Laws of Motion for class 9 are provided below.*

**(1) Which would exert a greater force to accelerate 5 kg mass at 2m/s ^{2} acceleration or 2 kg mass at 5 m/s^{2} acceleration?**

**Ans-**

**(2) Ram whose mass is 80 kg is going on his bike of 500 kg. He used brakes to stop the bike. He takes 2s to stop bike. Find the force exerted by the bike while velocity of the bike was 100 km/h?**

**Ans-**

**(3)Two balls of mass 10 kg and 20 kg are moving with a velocity of 5 m/s and 8 m/s in the same direction respectively. After collision they moved together. Find the combined velocity of them after collision.**

**Ans-**

**(4) A man wants to move a heavy stone at a distance of 5 m. He is trying to do it hard but not able to move. His friend suggests him to get some more people to move it. In your opinion is he right?**

**Ans-**

Friend of that man is right. The man should take help of some more people. Stone is pushing force on ground and ground is also pushing back stone with equal force in upward direction. A friction force is also exerting between ground and stone which is opposing motion of the stone. Therefore, man has to push stone with greater force or force more than friction force. For greater force he needs more people to push stone.

**(5) An object of mass 100 kg is accelerating from a velocity of 10m/s to 20m/s. Calculate change in momentum of the object.**

**Ans-**

**(6) An object is moving with velocity of 50 m/s and covered 10 km. Find the force applied on it if mass of the object is 200 kg.**

**Ans-**

**(7)Two children are going on the road .Mass of the first child is 50 kg and mass of the other child is 60kg and they are moving with the velocity of 10 m/s and 8 m/s respectively. Both are moving in opposite direction. If they collide what will be their combined velocity and also tell direction of their movement.**

**Ans-**

**(8) A tractor of mass 5000 kg is pulling two carts of mass 2000 kg each. Each cart is carrying 1000 kg load. Tractor is moving with velocity of 50 km/h I forward direction. He travels 10 km in 10 s. Find net force of the tractor. Find the momentum of the tractor.**

**Ans-**

**(9) F =ma is**

**(i) Newton’s first law of motion**

**(ii) Newton’s second law of motion**

**(iii) Newton’s third law of motion**

**Ans-**(ii) Newton’s second law of motion

**(10) Law of conservation of the momentum is**

**(i) m _{1}u_{1} + m_{2}u_{2} = m_{1}v_{1} + m_{2}v_{2}**

**(ii) mu =0**

**(iii) mv ^{2} +mu^{2} =mvs**

**Ans- **(i) m_{1}u_{1} + m_{2}u_{2} = m_{1}v_{1} + m_{2}v_{2}

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