Forces

A student investigated how changing the mass of a trolley affects the acceleration of the trolley. Figure 5 shows some of the equipment used. The trolley in Figure 5 is not moving. Which force prevents the trolley from moving?

The force pulling on the trolley was increased so that the trolley accelerated. The force was then kept constant and different masses were put on the trolley. For each different mass the acceleration of the trolley was measured. <br><br> Which of these is the independent variable?

Which of these is the dependent variable?

For one of the masses put on the trolley, the student recorded three values of acceleration: <br> 1.58 m/s², 1.53 m/s², 1.54 m/s² <br><br> Calculate the mean acceleration of the trolley.

Figure 6 shows some of the results. Describe the relationship shown in Figure 6.

When the total mass of the trolley was 1.5 kg, the acceleration of the trolley was 0.62 m/s². <br><br> Calculate the resultant force acting on the trolley. <br> Use the equation: <br> resultant force = mass × acceleration

Some quantities are scalar quantities and others are vector quantities. Which of the following is a scalar quantity?

Which of the following is another scalar quantity?

A person has been for a walk. Figure 9 shows the distance-time graph for the walk. What was the total distance walked by the person in 2000 seconds?

Calculate the average speed of the person during the 2000 seconds. Use your answer to Question 05.2. <br> Use the equation: <br> average speed = total distance / total time

Which section of Figure 9 shows the person walking the slowest? Give a reason for your answer.

The person walked slowest when going up some steps. Complete the sentence. Choose the answer from the box. <br><br> When walking up the steps, the person did more work against the force of __________.

On another day, the person ran the same route. What is a typical speed for a person running?

A swimming pool is being filled with water. Calculate the weight of the water in the swimming pool when the mass of the water is 25 000 kg. <br> gravitational field strength = 9.8 N/kg <br><br> Use the equation: <br> weight = mass × gravitational field strength

When the swimming pool is full, the weight of the water is 1 960 000 N. The bottom of the swimming pool has an area of 49 m². <br><br> Calculate the pressure at the bottom of the swimming pool when it is full. <br> Use the equation: <br> pressure = weight / area <br><br> Choose the unit from the box.

There is a force acting on the side of the swimming pool because of the water pressure. Figure 11 shows the side of the swimming pool. Which arrow shows the direction of the force acting on the side of the swimming pool?

A child is swimming in the pool. The velocity of the child is 0.70 m/s. The child then accelerates for 5.0 s, reaching a final velocity of 1.3 m/s. <br><br> Calculate the acceleration of the child. <br> Use the equation: <br> acceleration = change in velocity / time taken

Figure 12 shows a diving board at the side of the swimming pool. The original length of the spring is 0.84 m. When the child stands on the diving board, the length of the spring decreases by 0.21 m. <br><br> Calculate the percentage change in the length of the spring.

The force applied to the spring by the weight of the child is 336 N. The change in length of the spring is 0.21 m. <br><br> Calculate the spring constant of the spring.

The child steps off the diving board and falls into the swimming pool. The initial velocity of the child is 0 m/s. <br> acceleration due to gravity = 9.8 m/s² <br><br> Calculate the final velocity when the child has fallen a distance of 0.95 m through the air. <br> Give your answer to 2 significant figures. <br> Use the Physics Equations Sheet.

Figure 17 shows a young child using a baby walker. The child is standing still. What is the resultant vertical force on the child? Give a reason for your answer.

Use the Physics Equations Sheet to answer questions 09.2 and 09.3. <br><br> Write down the equation which links distance (s), force (F) and work done (W).

The child pushed the baby walker 2.8 m across a horizontal floor. The work done by the child was 35 J. <br><br> Calculate the horizontal force the child applied to the baby walker.

The child pushed the baby walker from a carpet onto a hard floor. The child applied the same horizontal force to the baby walker. Explain why the speed of the baby walker increased.

There are some toy gears on the front of the baby walker. The child applies a force to gear A. This causes a moment about the pivot, so gear A rotates. <br><br> Use the Physics Equations Sheet to answer questions 09.5 and 09.6. <br><br> Write down the equation which links distance (d), force (F) and moment of a force (M).

The child applies a force of 2.0 N on gear A. The perpendicular distance between the force and the pivot is 7.5 cm. <br><br> Calculate the moment of the force about the pivot.

Explain what happens to gear B when the child applies the force to gear A.

A child is standing still in a baby walker. What is the resultant vertical force on the child? Give a reason for your answer.

Write down the equation which links distance (s), force (F) and work done (W).

The child pushed the baby walker 2.8 m across a horizontal floor. The work done by the child was 35 J. Calculate the horizontal force the child applied to the baby walker.

The child pushed the baby walker from a carpet onto a hard floor. The child applied the same horizontal force to the baby walker. Explain why the speed of the baby walker increased.

There are some toy gears on the front of the baby walker. Figure 6 shows the gears. The child applies a force to gear A, which causes a moment about the pivot. Write down the equation which links distance (d), force (F) and moment of a force (M).

The child applies a force of 2.0 N on gear A. The perpendicular distance between the force and the pivot is 7.5 cm. Calculate the moment of the force about the pivot.

Explain what happens to gear B when the child applies the force to gear A.

A submarine descends from the surface of the sea. Explain what happens to the pressure on the submarine.

The submarine moved from the surface of the water to the bottom of the Mariana Trench. The change in pressure was 110 000 kPa. mean density of sea water = 1026 kg/m³ gravitational field strength = 9.8 N/kg Calculate the depth of the Mariana Trench. Use the Physics Equations Sheet.

A student investigated how the acceleration of a trolley varies with the resultant force on the trolley. Figure 10 shows some of the equipment used. Figure 10 shows the force F which acts through the string. What name is given to force F?

Give one variable that should have been a control variable in this investigation.

The student held the trolley stationary and then released it. The trolley moved along the runway with a constant acceleration. The student recorded the time taken for the trolley to travel a measured distance along the runway. Describe how the acceleration of the trolley can be calculated using the time taken and distance travelled by the trolley.

For one set of results, the force acting through the string was 2.0 N. The student released the trolley three times and determined the following values for acceleration: 1.36 m/s², 1.39 m/s², 1.33 m/s² Calculate the uncertainty in the values of acceleration.

The runway was then raised at one end. The force acting through the string remained the same. Explain how the acceleration was affected by raising the end of the runway.

Figure 12 shows a velocity-time graph for a train travelling between two stations. Determine the distance travelled by the train in the first 600 s of the journey.

Explain what happens to the braking force as the train decelerates. Use information from Figure 12.

Determine the maximum deceleration of the train.

Another train travels at a speed of 60 m/s. A constant braking force of 270 000 N causes the train to decelerate and stop. mass of train = 240 000 kg Calculate the distance travelled while the braking force is applied. Use the Physics Equations Sheet.

It is illegal for train drivers to drink alcohol before driving a train. Explain how drinking alcohol would affect the stopping distance of a train.