Resultant forces

Questions 9 and 10 refer to the information below.

9 Which of the following is a free-body force diagram for the ball at its maximum height?

Questions 4 and 5 refer to two small positively charged spheres S₁ and S₂ suspended by threads,

4 Which of the following vector diagrams shows the forces acting on S₂?

A B C D

Overhead electricity cables for railway lines are supported by structures like the one shown.

An electric cable of mass 45 kg is suspended from a support rod X. A second support rod Y is attached to X. X and Y are attached at one end to a column.

The masses of support rods X and Y are negligible.

Determine, by taking moments, the force exerted on rod X by rod Y.

Complete the free‑body force diagram for support rod X.

A website gives a value of the electric field strength E, at two distances from the

Deduce whether these data are consistent with an inverse square law.

The photograph shows a cyclist cycling at a constant velocity on horizontal ground.

The cyclist stops pedalling and comes to rest in a time of 5.2 s.

Sketch a graph to show how the cyclist’s velocity changes during this time.

Assume the deceleration is constant.

The cyclist travels 7.80 m while coming to rest.

Calculate the average resistive force on the cyclist and bicycle.

mass of cyclist and bicycle = 28.0 kg

A trapdoor is fixed to a vertical wall with a hinge. A wire is attached to the other end of the trapdoor and inclined at an angle of 60°, as shown. The wire holds the trapdoor horizontal.

Which of the following shows the free-body force diagram for the trapdoor?

In the game of golf a stationary ball is hit by a club. One of the aims of the game is to land the ball on a patch of ground called the green.

The graph shows how the force F exerted by the club on the ball varies with time t as the ball is hit.

State why the area under the graph represents impulse.

Show that the velocity of the ball is about 30 m s⁻¹ immediately after it is hit by the club.

mass of ball = 0.046 kg

The ball has a time of flight of 3.5 s before landing. The green is a vertical distance of 7.5 m above the point at which the ball was hit, as shown. The green is about seventy metres away from where the ball is hit.

Deduce whether, if air resistance is ignored, the ball could land on the green after a flight time of 3.5 s.

Scientists have been studying a type of jumping spider that can jump up to six times its body length.

The scientists photographed a spider at 0.02s intervals, during a jump. The picture is taken from the photograph and is shown actual size.

Deduce whether the images show that the motion in the x-direction is independent of the motion in the y-direction. You should take measurements using the cross marking the centre of gravity of the spider.

Show that the initial velocity of the spider at the start of the jump is about 1 m s⁻¹. You should take measurements using the cross marking the centre of gravity of the spider.

The spider achieves this jump by extending its two back legs by 3.0 mm.

Calculate the average force the spider exerts in each leg to achieve the jump.

mass of spider = 150 mg

Just as the spider starts the jump, it fixes a silk thread to the platform. It is thought that the thread acts as a safety line in case the spider falls.

A student makes the comment:

ʻIf the silk thread can withstand a tension equal to the weight of the spider then this safety system should work.ʼ

Deduce whether this statement is correct.

Scientists have been studying a type of jumping spider that can jump up to six times its body length.

The scientists photographed a spider at 0.02s intervals, during a jump. The picture is taken from the photograph and is shown actual size.

Deduce whether the images show that the motion in the x-direction is independent of the motion in the y-direction. You should take measurements using the cross marking the centre of gravity of the spider.

Show that the initial velocity of the spider at the start of the jump is about 1 m s⁻¹. You should take measurements using the cross marking the centre of gravity of the spider.

The spider achieves this jump by extending its two back legs by 3.0 mm.

Calculate the average force the spider exerts in each leg to achieve the jump.

mass of spider = 150 mg

Just as the spider starts the jump, it fixes a silk thread to the platform. It is thought that the thread acts as a safety line in case the spider falls.

A student makes the comment:

ʻIf the silk thread can withstand a tension equal to the weight of the spider then this safety system should work.ʼ

Deduce whether this statement is correct.

A current / and a magnetic field of flux density B are applied to a slice of semiconductor

Calculate the angle of the Earth’s magnetic field to the horizontal.