Newtons Laws 01

Which of the following is not one of Newton’s laws of motion?

• The total momentum of a system of interacting bodies remains constant, providing no external force acts.    

• The rate of change of momentum of a body is directly proportional to the external force acting on the body and take place in the direction of the force.   

• If a body A exerts a force on body B, then body B exerts an equal and oppositely-directed force on body A.

• A body continues in a state of rest or of uniform motion in a straight line unless acted upon by some external force.            

• For every action, there is an equal and opposite reaction. 

An aircraft is flying straight horizontal line with constant velocity relative to the ground. What is the resultant force acting on the aircraft?

• weight of the aircraft.

• As a result of the air resistance and the thrust of the engine.

• The resultant of the air resistance and weight of the aircraft.

• The thrust of the engine.

• zero.

A parachutist of mass 80 kg is descending at a constant velocity of 3.0 m s^-1. What is the resultant force acting on the parachutist?

• 800 N upwards

• 800 N downwards      

• 240 N upwards.          

• 240 N downwards

• zero.

A pendulum bob suspended from the ceiling of a train carriage is just above a mark on the carriage floor when the train is at rest. The train is then started moving with a constant velocity. Then the position of the bob?

• Behind the mark, so that the pendulum string is along the resultant of the force due to the motion of the train and gravity.

• Remains over the mark because the force due to the motion of the train is balanced by the reaction of the pendulum string on the supports.

• It is behind the mark in a position in which the horizontal force exerted by the train on the bob is balanced by the horizontal component of the tension in the pendulum string.

• In front of the mark because the inertial force is in the same direction as the train is moving.  

• Remains over the mark because the motion of the train produces no additional force on the bob.

A helicopter of mass 3000 kg is rising vertically with a constant velocity of 25 m s^‑1. The resultant force acting on the helicopter must be.

• zero    

• 30 000 N upwards.

• 30 000 N downwards.            

• 45 000 N downwards.

• 50 000 N upwards.

A tractor of mass 1000 kg tows a trailer of mass 1000 kg. The total resistance to the motion is   4000 N and one-quarter of this resistance acts on the trailer. The tractor and trailer are moving with a constant speed of 6 m s^‑1. What is the force exerted on the tractor by the tow bar?

• 500 N

• 1000 N

• 3000 N

• 4500 N

• 6000 N

Which of the following statements best describes the weight of an object?

• The gravitational potential energy of the object.

• the gravitational field acting on the object.

• the product of mass and acceleration due to gravity.

• the gravitational force acting on the object.

• the object’s mass multiplied by its acceleration.

The ball moving along the horizontal surface passes the edge at time T. which of the following graph shows the variation of the resultant vertical force acting on the ball with time from X to Y?

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A rear-wheel-drive car is accelerating in the direction shown.

Which of the following diagrams best shows the resultant force exerted on the rear wheels of the car?

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A man of mass m sits in a car that is accelerating horizontally at 0.5g. What is the magnitude of the resultant force (nearly) exerted by the seat on the man?