Physics Answers

The length of a pin hole camera 10.1 m. How far is an object 1m high placed from the pin hole for the image to be 0.025 m high.

. The activity of a source was measured as follows

Time/days 0 2 3 4 5

Activity 137 63 44 31 22

The background count was 7

i. Explain background count. How does it occur?

ii. Sketch the above graph and determine the half life of the source.

Discuss Thomson’s atomic model ( what was his proposal on how an atom looks like?).

Explain its failures.

mass of 5 000kg is taking off straight up from the surface of the Earth. How much upwards force do the rockets engine need to produce to cause the rocket to accelerate straight up at 15m/s2? 

What is the importance of Microwaves in radio astronomy

A non-insulated pipe passes through a room in which air and walls are at 25°C. The outside

diameter of the pipe is 70 mm, and its surface temperature and emissivity are 200°C and 0.8,

respectively. What are the surface emissive power and irradiation? If the coefficient associated

with free convection heat transfer from the surface is 15W/m2K, what is the rate of heat loss

from the surface per unit length of the pipe?

(E = 2270.48 W/m2

, G = 447.14 W/m2

, Q/l = 997.90 W/m)

A point charge 𝑞1 = +6.00 𝑥 10−9𝐶 is at the point 𝑥 = 0.800 𝑚, 𝑦 = 0.600 𝑚 and a second point charge 𝑞2 = −2.00 𝑥 10−9𝐶 is at the point 𝑥 = 0.800 𝑚, 𝑦 = 0 𝑚. Calculate the magnitude and direction of the resultant electric field at the origin due to these charges.

A point charge 𝑞 = 8.00 𝑥 10−9𝐶 is at the center of the cube with sides of length 0.200 m. What is the electric flux through one of the six faces of the cube?

A 1.6m tall man stands in front of a plane mirror.how tall is the image form

1. A 50-kg barbell is lifted at a height of 1.4m from the floor in 1.2 seconds. What is the work done? how much power is expended?

2. A 60 kg block at rest was pushed by a 100 N force on a frictionless horizontal.

A. what is the kinetic energy of the block at a distance of 8 meters?

B. what is the velocity of the blockat a distance of 8 meters?