Forces Practice Questions

Describe how the geologist could measure the weight of the rock sample in the laboratory.

Calculate the weight of the rock sample on Earth.

The rock sample is taken to the Moon, where the gravitational field strength is $1.6$ N/kg.

Calculate the weight of the rock sample on the Moon.

Which statement about the sledge is correct?

Put a cross ( ☒ ) in the box next to your answer.

☐ A The resultant force on the sledge is zero.

☐ B The resultant force on the sledge acts in the direction of motion.

☐ C The pulling force is greater than the friction force.

☐ D There is no friction acting on the sledge.

Explain, in terms of the horizontal forces acting on the sledge, why the sledge moves at a constant velocity.

Calculate the resultant force needed to give the drone a horizontal acceleration of $4.0$ m/s$^2$.

The drone picks up a parcel of mass $250$ g. The resultant force on the drone is now $2.0$ N.

Calculate the new acceleration of the drone.

The drone then hovers, staying at rest in the air above the delivery address.

Explain the size of the upward force produced by the drone's rotors while it hovers.

Explain why the ball has a changing velocity even though its speed is constant.

On Figure 1, draw an arrow to show the direction of the resultant force acting on the ball when it is at point P.

Name the force that provides the centripetal force on the ball.

Determine the size and direction of the resultant vertical force on the balloon at this moment.

size = ............................................... kN, direction is ...............................................

State the effect of this resultant force on the motion of the balloon.

Later in the flight the balloon rises at a constant velocity.

State the size of the resultant force on the balloon now and explain your answer using Newton's first law.

Calculate the acceleration of the car.

Calculate the resultant force acting on the car during this time.

The driving force produced by the car's engine stays constant, but the resistive forces on the car increase as it goes faster.

Explain what happens to the acceleration of the car as its speed increases.

Identify the anomalous result in the table.

Use the result for $F = 1.50$ N to calculate the total mass of the moving system.

The student did not slope the runway before taking the readings.

The value calculated in (b) is larger than the actual total mass of the trolley, hanger and weights.

Explain why.

Devise a method the student could use to investigate how the acceleration of the trolley depends on the accelerating force applied to it.

Your method should include:

• how the accelerating force is changed
• how the total mass of the moving system is kept constant
• how the acceleration is measured
• how the effects of friction are dealt with.

Calculate the weight of the rocket at the moment of launch.

Calculate the acceleration of the rocket at the moment of launch.

During the first few seconds after take-off the thrust from the engines stays constant, but the acceleration of the rocket increases.

Explain why.

State the size of the tension in the rope and explain your answer using Newton's first law.

A student says:

"The weight of the crate and the tension in the rope are a Newton's third law pair of forces."

Explain why the student is wrong.

The Earth pulls the crate downwards with a gravitational force of $320$ N.

State the force that forms a Newton's third law pair with this force.