Forces (Cambridge O Level Physics)

A bus drives along a flat road. Its engine produces a forward driving force of 7000 N. Drag forces, D also act on the bus.

The bus has an acceleration of 1.2 m/s² and a mass of 2500 kg.

What is the value of D?

The diagram shows four objects, each with a different mass. Each object is acted on by the forces shown.

Which object will experience the largest acceleration?

The graph below shows the journey of a truck along a straight, flat road.

During which part of the journey is the resultant force on the truck equal to zero?

A car is driving on a motorway at a constant speed of 70 miles per hour. 

The driver notices a queue of traffic up ahead and begins to slow down. 

Which diagram best describes the resultant force acting on the car as it slows down?

Extended

A plank is placed on the floor, with a weighty box on top of it, as shown in the diagram.

A force of 70 N is required to lift one end of the plank, while the other rests on the floor.

What is the weight of the plank, W?

A uniform beam is pivoted at one end and suspended by a 200 N force as shown in the diagram.

The beam is in equilibrium.

What is the weight of the beam?

A cardboard rectangle is hung from a nail as shown in the diagram.

A plumb line is also hung from the nail.

Which of the points labelled shows the centre of gravity of the cardboard rectangle?

A uniform beam of wood of mass  rests on a pivot. The far left side of the wood is tied to a bolt in the floor with a length of rope with tension , such that it lies completely horizontal. An object of mass is placed with its centre of gravity on the very end of the right hand side of the beam.

The perpendicular distance from the rope to the pivot is one quarter of the beam's length.

Which expression for the mass of the beam is correct?

A "V" shaped object has a sphere attached to either end of the "V" and is balanced on its point. The length of the short arm of the object is . The sphere of mass is a height  off the ground. The sphere of mass  is a horizontal distance of from the point of the shape. 

The object is in equilibrium. Which expression for is correct? 

A motorbike travels at a constant speed along a flat road. Three horizontal forces act on the motorbike. Two of them are shown in the diagram below.

What is the size and direction of the third force?

An object with three forces acting on it is shown below.

What is the resultant force acting on the object?

Two students were discussing Newton's first and second laws of motion. 

Which statement correctly summarises these two laws?

A car slows down as it approaches a traffic light. The car was traveling at 13.5 m/s and it takes 22 s to come to a stop. 

The mass of the car is 950 kg.

Calculate the force required to stop the car.

The diagrams below show three beams, each is pivoted at the centre. Each beam also has two forces acting on it, as shown.

Which of the beams will rotate clockwise?

A ‘yardarm’ is a stick, hung from a string, that is used to weigh goods. Goods are placed in the pan on the left, and weights are added to the box on the right side until it balances.

The weight of the pan and the box are such that the weight of the yardarm itself is entirely balanced by the pan.

The yardarm is 65 cm long.

How many 0.5 N weights need to be added to the box in order to balance the yardarm?

A plank rests on two supports, as shown in the diagram. The plank is in equilibrium. Three forces act on the plank.

Which statement is true?

A corkscrew is used to open a bottle of delicious wine.

An overworked teacher in self-isolation applies two forces at each of the positions shown below.

Which pair of forces produces the greatest turning force?

The diagram shows a door handle with three forces acting on it.

How will the door handle move?

The diagrams each show a beam resting on a pivot and being acted on by some forces. The beam is not attached to the pivot. The pivot is in the centre of the rod in each case.

Which of the beams is in equilibrium?

A wardrobe is shown tilted at a variety of angles.

In which position is the wardrobe in equilibrium?

Why are passengers not allowed to stand up on the top deck of a double decker bus?  

A coin falls from rest through the air and eventually reaches a constant speed. 

There is a resultant force acting on the coin due to the two forces P and Q shown in the diagram. 

What happens to force P and what happens to the resultant force before the coin reaches constant speed?

Which object has the largest resultant force acting on it?

A tractor pulls a trailer at a constant speed.

The tractor exerts a force of 1600 N forwards on the trailer.

What force is exerted by the trailer on the tractor?   

Which car experiences a resultant force that is not zero?

A horizontal beam is pivoted at X. A mass of 200 g rests on the beam as shown. The centre of mass of the beam is 50 cm from the right-hand end of the beam.

The beam is balanced. 

What is the mass of the beam?

A car is designed to be stable.

Where must the centre of gravity of the car be?