- A0.75 m/s
- B-0.75 m/s
- C1.5 m/s
- D-1.5 m/s
Using the Law of Conservation of Momentum: Initial momentum of (rifle + bullet) is 0. Final momentum m_bullet * v_bullet + m_rifle * v_rifle = 0. So, 0.010 kg * 150 m/s + 2 kg * v_rifle = 0. This gives 1.5 + 2 * v_rifle = 0, so v_rifle = -1.5 / 2 = -0.75 m/s. The negative sign indicates the direction opposite to the bullet.
More Questions on How Forces Affect Motion
1A car's engine generates a forward thrust of 5000 N. If the total frictional forces (air resistance + road friction) amount to 3000 N, and the car's mass is 1000 kg, what is the car's acceleration?
→ 2What is the recoil velocity of a fire extinguisher of mass 10 kg, if it ejects 0.05 kg of CO₂ per second with a velocity of 20 m/s?
→ 3A constant force 'F' is applied to an object, causing it to accelerate. If the mass of the object is doubled while the force remains the same, how does its acceleration change?
→ 4Differentiate between static friction and kinetic friction.
→ 5Which of the following describes the state of an object experiencing a balanced force?
→ 6How do airbags in cars enhance safety during a collision?
→ 7A billiard ball (A) moving at 5 m/s collides head-on with an identical stationary billiard ball (B). After the collision, ball A stops. What is the velocity of ball B immediately after the collision?
→ 8Why are racing cars designed to be low to the ground and have wide tires?
→ 9A force of 100 N is applied to a 20 kg mass at rest. After 5 seconds, the force is removed. What is the velocity of the mass at this instant?
→ 10Consider a book resting on a table. According to Newton's Third Law, the book exerts a downward force on the table. What is the reaction force to this?
→ 11Two identical balls, A and B, are dropped from the same height. Ball A experiences significant air resistance, while Ball B is in a vacuum. Which statement is true regarding their acceleration?
→ 12A block slides down a frictionless inclined plane. What causes its acceleration?
→ 13What is the relationship between force and change in momentum according to Newton's Second Law?
→ 14Which of the following scenarios demonstrates an object having inertia of motion?
→ 15How does wearing a helmet protect a person's head during a fall?
→ 16A spacecraft in orbit around Earth fires its thrusters. Why does the spacecraft accelerate in the opposite direction to the expelled gases?
→ 17A 50 g ball is dropped from a height of 5 m. What is its momentum just before it hits the ground? (Assume g = 10 m/s², neglect air resistance)
→ 18A 50 g ball is dropped from a height of 10 m. What is its momentum just before it hits the ground? (Assume g = 10 m/s², neglect air resistance)
→ 19A block is placed on an inclined plane. Describe the forces acting on the block if it remains at rest.
→ 20An object has a constant velocity. Which of the following statements is true about the forces acting on it?
→ 21Why does a fielder pull his hands back while catching a fast-moving cricket ball?
→ 22A hockey player pushes a puck of mass 0.15 kg with a force that lasts for 0.05 seconds. If the puck starts from rest and achieves a velocity of 30 m/s, what was the average force applied by the player?
→ 23Which of the following describes the relationship between mass and inertia?
→ 24Describe the concept of 'impulse' and its practical application in sports.
→ 25A 2 kg object is dropped from a height. What is the magnitude of the force acting on it due to gravity (take g = 9.8 m/s²)?
→ 26Why do astronauts experience weightlessness in space, even though there is still gravitational force acting on them?
→ 27When is the momentum of a system considered to be conserved?
→ 28A person rowing a boat pushes the water backward with their oars. The boat moves forward. This illustrates which of Newton's Laws?
→ 29What is the significance of the slope of a velocity-time graph in determining the force acting on an object?
→ 30A 10 kg block is initially at rest on a frictionless horizontal surface. A horizontal force of 30 N is applied to it for 4 seconds. What is the final momentum of the block?
→ 31Explain why it is easier to pull a lawnmower than to push it.
→ 32An object thrown vertically upwards reaches its maximum height and momentarily stops. What is the net force acting on the object at that exact instant?
→ 33A force of 10 N acts on an object, displacing it by 5 m in the direction of the force. How much work is done by the force?
→ 34Two cars, A and B, collide. Car A has a mass of 1000 kg and is moving at 10 m/s. Car B has a mass of 1500 kg and is moving at 7.5 m/s in the opposite direction. After a head-on collision, they stick together. What is their common velocity?
→ 35Two cars, A and B, collide. Car A has a mass of 1000 kg and is moving at 10 m/s. Car B has a mass of 1500 kg and is moving at 5 m/s in the opposite direction. After a head-on collision, they stick together. What is their common velocity?
→ 36How does the concept of inertia explain why a heavy stone is harder to kick than a football?
→ 37An object of mass 4 kg is acted upon by two forces: 10 N to the right and 2 N to the left. What is the acceleration of the object?
→ 38Why are car seatbelts crucial for safety during a sudden stop?
→ 39A person holds a book stationary in their hand. Identify the action-reaction pair related to gravity acting on the book.
→ 40A hammer of mass 1 kg, moving at 10 m/s, strikes a nail. The nail stops the hammer in 0.01 seconds. What is the force exerted by the nail on the hammer?
→ 41A car travels around a circular track at a constant speed. Is there a net force acting on the car? Explain.
→ 42What is the primary difference between balanced and unbalanced forces in terms of their effect on an object's motion?
→ 43A constant force acts on an object of mass 5 kg for 2 seconds, increasing its velocity from 3 m/s to 7 m/s. Find the magnitude of the applied force.
→ 44Why is it dangerous to jump out of a moving train?
→ 45Explain the principle of conservation of momentum with an example.
→ 46What is the momentum of a 500 g object moving at a velocity of 20 cm/s?
→ 47An object of mass 1 kg is moving at a speed of 10 m/s. A constant opposing force of 2 N acts on it. How long will it take for the object to come to rest?
→ 48Describe the role of friction in everyday activities, giving one beneficial and one detrimental example.
→ 49A block is at rest on a table. Which of the following statements about the forces acting on it is true?
→ 50Why does a karate player break a slab of ice with a single blow?
→ 51Explain the concept of 'unbalanced force' and its effect on an object's motion.
→ 52A bowler pushes a bowling ball (mass 6 kg) with a force of 18 N. What is the acceleration of the ball?
→ 53What would happen if an object with significant mass was thrown in space (far from any gravitational pull) with an initial velocity?
→ 54Assertion: It is difficult to balance oneself on a bicycle that is at rest. Reason: The rotational inertia of the wheels keeps the bicycle stable when it is moving.
→ 55An object of mass 20 kg is accelerated uniformly from 5 m/s to 15 m/s in 4 seconds. Calculate the magnitude of the force applied.
→ 56Describe a situation where a body is moving but the net force acting on it is zero.
→ 57What is the unit of impulse, and how is it related to momentum?
→ 58A student drops a ball from the top of a building. At the same instant, another student throws an identical ball horizontally from the same height. Which ball will hit the ground first, assuming no air resistance?
→ 59In a game of tug-of-war, if Team A is pulling with a force of 500 N and Team B is pulling with a force of 450 N, what is the net force acting on the rope, and in which direction?
→ 60Which of Newton's laws of motion quantifies the force required to change an object's state of motion?
→ 61A force of 20 N is applied to an object of mass 5 kg, initially at rest, for 3 seconds. What is the final velocity of the object?
→ 62How does the presence of air resistance affect the acceleration of a falling object?
→ 63A body of mass 'm' is dropped from a height 'h'. What is the force acting on the body just before it hits the ground, neglecting air resistance?
→ 64When a person walks, they push on the ground, and the ground pushes back, propelling them forward. Identify the action and reaction forces in this scenario.
→ 65Explain why it is harder to change the direction of motion of a moving truck than a moving bicycle, assuming they have the same speed.
→ 66What is the relationship between force, mass, and acceleration as described by Newton's Second Law of Motion?
→ 67An astronaut outside a spacecraft throws a wrench. In what direction will the astronaut move?
→ 68Compare the concept of inertia for a stationary object versus a moving object.
→ 69A spacecraft is moving in deep space with its engines shut off. What will happen to its motion?
→ 70What is the impulse experienced by a 5 kg object if its velocity changes from 10 m/s to 4 m/s in the same direction?
→ 71A person experiences a greater impact when jumping onto a concrete floor compared to jumping onto a thick mat from the same height. Explain why.
→ 72An object of mass 'm' is moving with a constant velocity 'v'. If a constant force 'F' is applied to the object in the direction of its motion, how does its momentum change over time 't'?
→ 73Why does a gun recoil when a bullet is fired?
→ 74A student is attempting to push a heavy box across a rough floor. The student applies a force of 100 N, but the box does not move. What can be inferred about the frictional force acting on the box?
→ 75A boy of mass 40 kg jumps with a horizontal velocity of 5 m/s onto a stationary cart of mass 20 kg with frictionless wheels. What is their common velocity after the boy jumps on the cart?
→ 76Which of the following scenarios demonstrates an application of Newton's Third Law of Motion?
→ 77A soccer ball is kicked with an initial velocity of 15 m/s at an angle. Ignoring air resistance, what force causes the ball to eventually fall back to the ground?
→ 78Differentiate between mass and weight of an object.
→ 79A feather and a stone are dropped simultaneously from a height in a vacuum. Which one will reach the ground first?
→ 80Two bodies of masses m₁ and m₂ are moving with velocities v₁ and v₂ respectively. They collide and stick together, moving as a single body. What is their common velocity after the collision?
→ 81Explain how Newton's Third Law of Motion is demonstrated when a rocket takes off.
→ 82Assertion: A force acting on an object can change its speed, direction, or both. Reason: Force is a vector quantity that causes an acceleration.
→ 83A car of mass 1000 kg is moving with a velocity of 72 km/h. If the braking force applied by the brakes is 5000 N, calculate the distance the car travels before coming to rest.
→ 84Why is it more difficult to stop a heavily loaded truck than a small car moving at the same speed?
→ 85A passenger standing in a moving bus falls backward when the bus suddenly accelerates. Which principle of motion explains this phenomenon?
→ 86A cricket ball of mass 150g is moving with a velocity of 12 m/s. It is hit by a bat so that its velocity changes to 20 m/s in the opposite direction. If the bat is in contact with the ball for 0.01 seconds, what is the average force exerted by the bat on the ball?
→ 87When a balloon is inflated and then released, it flies around. This phenomenon is best explained by:
→ 88A car moves at a constant speed on a straight road. What can be concluded about the forces acting on the car?
→ 89The mass of an object is 10 kg. What is its weight on Earth (g = 9.8 m/s²)?
→ 90Which of the following forces is responsible for making objects fall to the Earth?
→ 91A force of 10 N acts on an object, causing it to accelerate at 2 m/s². What would be the acceleration if a force of 20 N acted on the same object?
→ 92According to the second law of motion, an object will accelerate when:
→ 93If an object is moving at a constant speed in a circular path, its velocity is:
→ 94A pitcher throws a baseball. As the ball leaves the pitcher's hand, it has a certain momentum. Which force primarily acts to change this momentum later?
→ 95A book lying on a table is an example of:
→ 96Why are seatbelts essential in cars?
→ 97A force of 50 N acts on a body for 0.5 s. What is the impulse produced?
→ 98What is the relationship between impulse and momentum?
→ 99The force required to change the state of motion of an object is called:
→ 100Which concept was first introduced by Galileo Galilei?
→ 101When you throw a ball upwards, what happens to its momentum as it goes up?
→ 102If the velocity of an object is constant, then its acceleration is:
→ 103A fisherman tries to push his boat away from the bank. He applies force on the bank and the boat moves away. This is an example of:
→ 104Which of the following statements is incorrect?
→ 105When a force is applied to an object, its momentum changes from p1 to p2 over a time interval t. The force applied is:
→ 106A heavy object has more inertia than a light object because it has:
→ 107The SI unit of momentum is also equivalent to:
→ 108A passenger is sitting in a bus. When the bus driver applies the brakes suddenly, the passenger tends to fall forward. This is due to:
→ 109What is the momentum of a stationary object?
→ 110In the absence of air resistance, a feather and a stone dropped from the same height will:
→ 111The unit of mass is:
→ 112If an object experiences a net force, it will:
→ 113The tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called:
→ 114Which statement is true for action and reaction forces?
→ 115A cart of mass M is moving with velocity V. If a mass m is added to the cart, the new velocity of the cart will be:
→ 116Newton's First Law defines:
→ 117Which of the following would require the largest force to accelerate?
→ 118When a car takes a sharp turn, passengers are thrown sideways due to:
→ 119The change in momentum of an object is equal to the:
→ 120A force of 20 N produces an acceleration of 4 m/s² in an object. What is the mass of the object?
→ 121What is the unit of impulse?
→ 122When you push against a wall, the wall pushes back on you with an equal and opposite force. This illustrates:
→ 123The principle of conservation of momentum applies to:
→ 124An object is said to have uniform velocity if it covers:
→ 125A fielder catching a fast-moving cricket ball often moves his hands backward with the ball. This is done to:
→ 126The formula for momentum is:
→ 127Which of the following is a non-contact force?
→ 128In an isolated system, two objects collide. Which of the following is true?
→ 129Galileo's experiment on the inclination of planes suggested that:
→ 130A force can change the:
→ 131What is the momentum of a 10 kg object moving with a velocity of 5 m/s?
→ 132A body of mass 5 kg is accelerated by a force of 20 N. The acceleration produced is:
→ 133A boy jumps out of a moving boat. What happens to the boat?
→ 134The property of matter that defines its resistance to changes in motion is:
→ 135If the mass of an object is doubled, its inertia will:
→ 136A force of 10 N acts on an object of mass 2 kg. What is the acceleration produced?
→ 137Which of the following is not a consequence of Newton's Third Law?
→ 138Impulse is defined as:
→ 139A rocket works on the principle of:
→ 140If an object is moving with constant velocity, the net force acting on it is:
→ 141What is the S.I. unit of acceleration?
→ 142A passenger standing in a bus falls backward when the bus starts suddenly. This illustrates:
→ 143The force which opposes the relative motion between two surfaces in contact is called:
→ 144A cricketer pulls his hands back while catching a ball. This helps to:
→ 145The rate of change of momentum of an object is proportional to the:
→ 146If no external force acts on a system, its momentum remains:
→ 147Action and reaction forces:
→ 148A hockey player hits a ball towards the goal. The ball continues to move towards the goal even after the stick is removed. This is due to:
→ 149Which of the following has the most inertia?
→ 150The law of conservation of momentum states that:
→ 151A body is said to be in uniform motion if it travels:
→ 152What is the approximate value of 1 Newton?
→ 153The force of friction always acts:
→ 154When a car suddenly stops, passengers tend to lean forward due to:
→ 155An object of mass 'm' moving with velocity 'v' has momentum 'p'. If the velocity is doubled, its momentum will be:
→ 156According to Newton's Second Law of Motion, Force is equal to:
→ 157Which of the following quantities is a vector quantity?
→ 158A bullet fired from a gun experiences a recoil. This is an example of:
→ 159The S.I. unit of momentum is:
→ 160If a net force acts on an object, the object will:
→ 161Newton's First Law of Motion is also known as:
→ 162The tendency of an object to resist a change in its state of motion is called:
→ 163A balanced force results in:
→ 164Which of the following is an example of a contact force?
→ 165What is the S.I. unit of force?
→ 166How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Take its downward acceleration as 10 m/s².
→ 167Akhtar, Kiran and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Akhtar and Kiran started pondering over the situation. Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. And as a result the insect died. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. Comment on these suggestions.
→ 168An object of mass 100 kg is accelerated uniformly from a velocity of 5 m/s to 8 m/s in 6 s. Calculate the initial and final momentum of the object. Also, find the magnitude of the force exerted on the object.
→ 169An object of mass 1 kg travelling in a straight line with a velocity of 10 m/s collides with and sticks to a stationary wooden block of mass 5 kg. Then they both move off together in the same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.
→ 170A bullet of mass 10 g travelling horizontally with a velocity of 150 m/s strikes a stationary wooden block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block and also calculate the magnitude of the force exerted by the block on the bullet
→ 171A hockey ball of mass 200 g travelling at 10 m/s is struck by a hockey stick so as to return it along its original path with a velocity of 5 m/s. Calculate the magnitude of change of momentum that occurred in the motion of the hockey ball due to the force applied by the hockey stick.
→ 172According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.
→ 173Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?
→ 174What is the momentum of an object of mass m, moving with a velocity v? (a) (mv)² (b) mv² (c) ½ mv² (d) mv
→ 175An automobile vehicle has a mass of 1500 kg. What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7 m s–2?
→ 176A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, then calculate: (a) the net accelerating force and (b) the acceleration of the train.
→ 177A stone of 1 kg is thrown with a velocity of 20 m s–1 across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice?
→ 178A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 tonnes
→ 179A batsman hits a cricket ball which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows to a stop because (a) the batsman did not hit the ball hard enough. (b) velocity is proportional to the force exerted on the ball. (c) there is a force on the ball opposing the motion. (d) there is no unbalanced force on the ball, so the ball would want to come to rest.
→ 180When a carpet is beaten with a stick, dust comes out of it, Explain
→ 181Why is it advised to tie any luggage kept on the roof of a bus with a rope?
→ 182An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on
→ 183Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?
→ 184Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.
→ 185In the following example, try to identify the number of times the velocity of the ball changes: “A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team”. Also identify the agent supplying the force in each case.
→ 186Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five rupees coin and a one-rupee coin?
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