Other Physics Answers

If 3/4 of a rope is 150 mm how long is the entire rope

a) The temperature of 200 g of water increases from 20°C to 50°C in 10 minutes. Calculate:

i. the amount of heat gained by the water.  

ii. the average rate at which the water is gaining heat.    

  (Specific heat capacity of water = 4200 J kg^{-1 O}C^-1)

b) Determine the amount of heat that must be removed from 1 kg of water at 40°C to convert it to ice at -5°C.

b) A man who has a mass of 80 kg can run up a flight of stairs of 20 steps, in 5 seconds. Given that each step is 20 cm high, how much power does the man use to run up the flight of stairs?

a) An object of mass 3 kg is dropped from the roof of a two-storey house and reaches the ground with a speed of 10 m/s. Neglecting friction, calculate:

i. the kinetic energy of the object when it reaches the ground.

ii. the potential energy of the object when it is on the roof.

iii. the height of the roof.

iv. the total mechanical energy of the object when it is 1 m above the ground.

A KTM commuter train travels between two stations, A and B. The train starts from rest from station A and accelerates at a constant rate for 0.5 km until it reaches a speed of 30 m/s. It then travels at this constant speed for T s before decelerating at a constant rate of 1.5 m/s² and coming to rest at station B. Figure 1 shows the velocity-time graph of the train’s journey between the two stations. Determine the value of T if the distance between the two stations 6 km. Calculate also the total time taken for the whole journey.

a 20.0 kg box is pulled horizontally 9.0 m along a level frictionless surface at a constant velocity. How much work is done on the box?

A car approaches a stationary police car at 36 m/s. The frequency of the siren (relative to the police car) is 500 Hz. What is the frequency (in Hz) heard by an observer in the moving car as he approaches the police car? (Assume the velocity of sound in air is 343 

m/s.)

QUESTION 1

a) Estimate the volume of the earth in m3 by assuming that its radius is 6400 km.

b) A car accelerates from zero to 20 m/s in 5 s. 

i.

Calculate the acceleration of the car.

ii.

If the acceleration is assumed to be constant, how far will the car travel in 15 s?

iii.

Calculate the speed of the car after 15 s.

A box of material X changes volume from 8.75 m³ to 10.0 m³ , when temperature is raised from 42.0 °C to 144 °C. Mass of the box is 12.0 kg.

(a) Calculate the volume expansion coefficient of the material.

(b) Calculate the change in density of the box, if temperature changes by 248 °C and initial volume is 10.0 m³.

3. Determine the image distance and image height for a 5.00-cm tall object placed 20.0 cm

from a concave mirror having a focal length of 15.0 cm.