Revision Chapter 6 PDF

Preview

Summary

Revision Chapter 6...

Description

Revision Ch. 6 [51 marks] 1.

2.

Newton’s law of gravitation A.

is equivalent to Newton’s second law of motion.

B.

explains the origin of gravitation.

C.

is used to make predictions.

D.

is not valid in a vacuum.

A mass at the end of a string is swung in a horizontal circle at increasing speed until the string breaks.

[1 mark]

[1 mark]

The subsequent path taken by the mass is a

3.

A.

line along a radius of the circle.

B.

horizontal circle.

C.

curve in a horizontal plane.

D.

curve in a vertical plane.

A horizontal disc rotates uniformly at a constant angular velocity about a central axis normal to the plane of the disc.

[1 mark]

Point X is a distance 2 L from the centre of the disc. Point Y is a distance L from the centre of the disc. Point Y has a linear speed v and a centripetal acceleration a. What is the linear speed and centripetal acceleration of point X?

4.

A pendulum bob is attached to a light string and is swinging in a vertical plane.

[1 mark]

At the lowest point of the motion, the magnitude of the tension in the string is A. less than the weight of the mass of the pendulum bob. B. zero. C. greater than the weight of the mass of the pendulum bob. D. equal to the weight of the mass of the pendulum bob.

5.

A particle P is moving anti-clockwise with constant speed in a horizontal circle.

[1 mark]

Which diagram correctly shows the direction of the velocity vand acceleration aof the particle P in the position shown?

6.

An aircraft is flying at constant speed in a horizontal circle. Which of the following diagrams best illustrates the forces acting on the aircraft in the vertical plane?

[1 mark]

7.

For a particle moving at constant speed in a horizontal circle, the work done by the centripetal force is

[1 mark]

8.

A.

zero.

B.

directly proportional to the particle mass.

C.

directly proportional to the particle speed.

D.

directly proportional to the (particle speed) 2.

The mass of Earth is ME, its radius is RE and the magnitude of the gravitational field [1 mark] strength at the surface of Earth is g. The universal gravitational constant is G. The ratio g is equal to G

9.

A.

ME R2E

B.

R2E ME

C.

ME RE

D.

1

A communications satellite is moving at a constant speed in a circular orbit around Earth. At any given instant in time, the resultant force on the satellite is

[1 mark]

A.

zero.

B.

equal to the gravitational force on the satellite.

C.

equal to the vector sum of the gravitational force on the satellite and the centripetal force.

D.

equal to the force exerted by the satellite’s rockets.

An electron moves in circular motion in a uniform magnetic field.

The velocity of the electron at point P is 6.8 × 10 5m s

–1in

the direction shown.

The magnitude of the magnetic field is 8.5 T. 10a. State the direction of the magnetic field.

[1 mark]

10b. Calculate, in N, the magnitude of the magnetic force acting on the electron.

[1 mark]

10c. Explain why the electron moves at constant speed.

[1 mark]

10d. Explain why the electron moves on a circular path.

[2 marks]

The diagram below shows part of a downhill ski course which starts at point A, 50 m above level ground. Point B is 20 m above level ground.

A skier of mass 65 kg starts from rest at point A and during the ski course some of the gravitational potential energy transferred to kinetic energy. 11a. From A to B, 24 % of the gravitational potential energy transferred to kinetic energy. Show that the velocity at B is 12 m s –1.

[2 marks]

11b. Some of the gravitational potential energy transferred into internal energy of the skis, slightly increasing their temperature. Distinguish between internal energy and temperature.

[2 marks]

11c. The dot on the following diagram represents the skier as she passes point B. Draw and label the vertical forces acting on the skier.

[2 marks]

11d. The hill at point B has a circular shape with a radius of 20 m. Determine whether the skier will lose contact with the ground at point B.

[3 marks]

11e. The skier reaches point C with a speed of 8.2 m s m at point D.

–1

. She stops after a distance of 24

Determine the coefficient of dynamic friction between the base of the skis and the snow. Assume that the frictional force is constant and that air resistance can be neglected.

[3 marks]

At the side of the course flexible safety nets are used. Another skier of mass 76 kg falls normally into the safety net with speed 9.6 m s –1. 11f. Calculate the impulse required from the net to stop the skier and state an appropriate unit for your answer.

[2 marks]

11g. Explain, with reference to change in momentum, why a flexible safety net is less likely [2 marks] to harm the skier than a rigid barrier.

12a. (i) Define gravitational field strength. (ii) State the SI unit for gravitational field strength.

[2 marks]

12b. A planet orbits the Sun in a circular orbit with orbital period T and orbital radius R. The [4 marks] mass of the Sun is M. 4π R (i) Show that T = √ GM . 2

3

(ii) The Earth’s orbit around the Sun is almost circular with radius 1.5×10 mass of the Sun.

11m.

Estimate the

This question is about gravitation and uniform circular motion. Phobos, a moon of Mars, has an orbital period of 7.7 hours and an orbital radius of

9.4 × 103 km . 13a. Outline why Phobos moves with uniform circular motion.

[3 marks]

13b. Show that the orbital speed of Phobos is about 2 km s−1 .

[2 marks]

13c. Deduce the mass of Mars.

[3 marks]

This question is about circular motion. The diagram shows a car moving at a constant speed over a curved bridge. At the position shown, the top surface of the bridge has a radius of curvature of 50 m.

14a. Explain why the car is accelerating even though it is moving with a constant speed.

[2 marks]

14b. On the diagram, draw and label the vertical forces acting on the car in the position shown.

[2 marks]

14c. Calculate the maximum speed at which the car will stay in contact with the bridge.

[3 marks]

© International Baccalaureate Organization 2019 International Baccalaureate® - Baccalauréat International® - Bachillerato Internacional®

Printed for Kolding Gymnasium...