Physics Answers

Let the force of gravity to be constant for small distances above the surface of the earth. A body is dropped from rest at a height h above the earth surface. What will be its kinetic energy just before it strikes the ground?

Four Minute Mile. As part of your training regiment for your eventual pro sports career, you are attempting to complete the famous “4-minute mile”, completing 4 laps of a 400 m track (which is not quite a mile, but it’s close) in a time of 4 minutes or less. As part of your training, you have been running several 3250 m races to improve your sustained long distance speed, and have completed them in an average time of 500 seconds. You have also run several 200 m sprints to improve your sprinting speed, and have completed those sprints in an average time of 25.0 seconds.

a) What are your average sustained long distance speed, and your average sprinting speed? (4)

b) Assuming that you run uniformly at the sustained speed from part a) for the first part of the race, and sprint at the sprinting speed from a) for the final part of the race, at what time should you start sprinting in order to complete the 1.60 km race in 4.00 minutes? How much distance have you covered in this time?

Assume the Ecodrain system (https://ecodrain.ca/en/products/A1000/) is 46% efficient.

a) If installed for greywater coming from the shower only, how much energy (in GJ) would it save per year in an average household?

b) How much does this amount of energy cost using today’s cost of electricity in BC ($0.0935/kWh if E < 1354 kWh and $0.1403 /kWh if E > 1354 kWh). Calculate it for both rates of energy.

c) How many years would it take for the Ecodrain system to pay for itself using today’s cost of an Ecodrain A1000.

A cable exerts a constant upward tension of magnitude 2.5 x 10⁴ N on a fully loaded elevator with a mass of 1.8 x 10³ kg as it rises to a vertical distance of 25.5 m.

A stationary observer heard an ambulance’s frequency 25 Hz lower than the 750 Hz at which it is emitted. If the air temperature is 20.0°c, how fast is the ambulance going?

A ship keel plate is 5.25m x 1.85m. Determine the maximum force on the plate when the ship is in fresh water at draught (height) of 6.14

Gilbert and Lando are pulling two ends of a rope on a frictionless floor with a distance of 15 m. Gilbert weighs 75 kg, and Lando weighs 60 kg. Suppose there is a flag marker between them. Find the center of mass of Gilbert and Lando.

Suppose you are standing on a frozen pond while carrying three wooden blocks that weigh 3.0 kg each. You need to horizontally throw each block away from you at a rate of 5.0 m/s to be able to get to the shore of the pond. Assuming that your mass is 65.0 kg, how fast are you moving after you throw the first block?

A radar signal took 5.1s to go to mars and return. How far away was Mars at that moment

a string is wrapped around a uniform homogeneous 3 kg solid cylinder with a 15 cm radius. The free end is attached to the ceiling from which the cylinder is then allowed to fall, starting from rest. As the string unwraps, the cylinder revolves.

a) what is the linear acceleration of the center of mass?

b) what is the linear velocity of the outer edge of the cylinder after a drop of 2m?

c) How fast is the cylinder revolving after a drop of 2m?

d) what is the tension in the chord?