4 Forces 2021 JnN

A spring, which obeys Hooke’s law, has an unstretched length of 10 cm.

A load of 20 N is suspended from the spring.

The new length of the spring is 36 cm.

What is the spring constant k of the spring?

• 0.56 N/cm

• 0.77 N/cm

• 1.3 N/cm

• 1.8 N/cm

The diagram shows the vertical forces acting on a toy rocket as it leaves the ground.

Calculate the size of the resultant vertical force on the rocket.

• 55 N

• 25 N

• 80 N

• 100 N

The diagram shows a solid object on a flat surface, with two forces acting on the object.

What is the resultant force on the object?

• 1 N to the left

• 1 N to the right

• 7 N to the left

• 7 N to the right

The extension–load graph for a spring is shown.

The unstretched length of the spring is 17.0 cm.

When an object is suspended from the spring, the length of the spring is 19.2 cm. What is the weight of the object?

• 1.4 N

• 1.6 N

• 2.6 N

• 3.0 N

A toy car travels down a sloping ramp at constant speed. Which statement about the forces acting on the car is correct?

• There are no forces acting on the car vertically.

• There is no resultant force acting on the car.

• There is no gravitational force acting on the car.

• There is no frictional force acting on the car.

A train travels at a constant speed along a straight track. Which statement about the resultant force on the train is correct?

• It is bigger than the thrust of the engine.

• It is constantly increasing.

• It is equal to the thrust of the engine.

• It is zero.

A cart has a mass of 10 kg. A boy pushes on the cart horizontally with a force of 50 N.

The cart accelerates at 0.50 m/s².

What is the frictional force acting on the cart?

• 5.0 N

• 20 N

• 30 N

• 45 N

A satellite orbits the Earth in an anticlockwise direction at constant speed, as shown.

When the satellite is in the position shown, in which direction does the resultant force act upon it?

• A

• B

• C

• D

A car of mass 1200 kg is travelling along a horizontal road.

Total frictional force = 1000 N

Driving force = 4000 N

What is the acceleration of the car?

• 0.83 m/s²

• 1.2 m/s²

• 2.5 m/s²

• 3.3 m/s²

The diagram shows a bird in flight.

The bird is flying in a horizontal direction to the right.

In which direction does air resistance act on the bird?

• A

• B

• C

• D