February 27, 2017

Homework Help: phy

Posted by christ on Monday, January 28, 2013 at 3:34am.

1 What is the gravitational field strength at a height h above the surface of the Earth? R is the radius of the earth

2 The instrument used for experimental determination of the value of the universal gravitational constant G is called
Galilio’s telescope
ballistic pendulum
Newton’s balance
Cavendish balance

3 At what altitude above the earth's surface would the acceleration due to gravity be 49ms−2? Assume the mean radius of the earth is 64106 metres and the acceleration due to gravity 98ms−2 on the surface of the earth

4 A man weighs 750 N on the surface of the earth. What would be his weight when standing on the moon? The masses of the earth and the moon are respectively, 5981024kg and 7361022kg. Their radii are respectively 637103km and 174103km
200.5 N
123.7 N
550.4 N
1000.0 N

5 A 2000 kg satellite orbits the earth at a height of 300 km. What is the speed of the satellite and its period? Take G=66710−11Nm2kg2, Mass of the earth is 5981024kg
7.73 km/s and 54103s
855.4km/s and 77104s
497.2km/s and 55105s
322.3km/s and 43104s

6 What is the orbital radius and speed of a synchronous satellite which orbits the earth once every 24h? Take G=66710−11Nm2kg2, Mass of the earth is 5981024kg
42107m and 3100 m/s
56106m and 4300 m/s
43108m and 5000 m/s
34107m and 6000 m/s

7 Given that the mass and radius of Jupiter are respectively 1901027kg and 715104km, calculate the escape velocity from the surface of the planet
11.2 km/s
33.3 km/s
59.5 km/s
110.4 km/s

8 A ball of mass 50 g tied to the end of a 50 cm inextensible string is whirled around in a vertical circle. Find the tension in the string when the ball is at the top of the circle. Take g=10ms2
70.7 N
20.4 N
39.5 N
96.3 N

9 An upward force of 12104N acts on an elevator of mass 20103kg. Calculate the acceleration of the elevator. Take g=98ms−2
38ms2 downward
47ms2 upward
38ms2 upward
47ms2 downward

10 A 40 N force applied at an angle of 37 degrees above the horizontal pulls a 5-kg box on a horizontal floor. The acceleration of the box is 3ms2. How large a fritional force must be retarding the motion of the box?
50 N
13 N
17 N
25 N

11 A block of mass 2 kg is connected to a freely hanging block of mass 4 kg by a light and inextensible string which passes over pulley at the edge of a table. The 2 kg mass is on the surface of the table assumed to be smooth. Calculate the acceleration of the system and the tension in the string
67ms2 and 13.3 N
33ms2 and 34.4 N
054ms2 and 40.6 N
25ms2 and 32.2 N

12 A 20 kg block on an inclined plane is pulled up the plane with rope tied to the block. The rope is at angle of 37 degrees above the surface of the plane. The tension in the rope is 250 N and the frictional force on the block is 8.0 N.What is the acceleration of the block?

13 A 15 kg block rests on the surface of a plane inclined at an of 30 degrees to the horizontal. A light inextensible string passing over a small, smooth pulley at the top of the plane connects the block to another 13 kg block hanging freely. The coefficient of kinetic friction between the 15 kg block and the plane is 0.25. Find the acceleration of the blocks.

14 A 2 kg and a 4 kg hang freely at opposite ends of a light inextensible string which passes over a small and light pulley fixed to a rigid support. Calculate the acceleration of the system.

15 Which of the following quantities has the same dimensions as work?
moment of a force

16 Which of the following is not true?
A crate sliding across the floor does work against frictional forces
Work is done if a component a force acting on an object exists in the direction of its displacement
A man with a bag of cement on his head does work to move the bag of cement as he walks from place to place on a flat horizontal floor
Work is a scalar quantity

17 Which of the following properties of a ball is conserved as it falls freely in a vacuum?
kinetic energy
gravitational potential energy
mechanical energy

18 How much work is done when a bucket of mass 1.5 kg with 10 kg of water in it is pulled up from the bottom of a well 8 m deep? Take g=98ms2
100.3 J
2000.5 J
901.6 J
453.7 J

19 A 65 kg sprinter completes a 100 m race in 9.83 s. Calculate the average kinetic energy of the sprinter
3.36 kJ
2.11 kJ
34.15 kJ
65.42 kJ

20 Which of the following is NOT a unit of energy?

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