# Kinematics and Energy

Could you provide workings out and answers to the following physics questions:

1.a. What is the difference between a scalar and a vector quantity?

b. A hiker walks due north for 4.0 km to reach point A and then northeast for 6.0 km to reach point B. Find by calculation or by scale drawing:

- the straight line distance from starting point to B

- the direction from the starting point to

- the average velocity of the hiker if the whole walk takes 2 hours

- the average speed of the hiker if the whole walk takes 2 hours

2. A car moves forward at 54 km/hr for 60 seconds, and then reverses at 18 km/hr for 30 seconds.

a. Sketch a velocity-time graph for this motion

b. Calculate the displacement of the car fro its starting position

c. Sketch a distance-time curve for the motion.

3. A cyclist rides for 100 seconds at a steady speed of 40 m/s up a hill sloping up at 10 degrees

a. If the cyclist and bicycle weighs 85 kg calculate their gain in potential energy over this period

b. If the cyclist's energy output is 2.0 kW over this period calculate the total work done

c. What fraction of the work is:

- converted into potential energy

- converted into kinetic energy

- done against friction

4. Two 60 ohm light bulbs are connected to a 240V supply:

a. Calculate the current if they are connected in series

b. Calculate the current if they are connected in parallel

c. In each case calculate the power consumed by ONE bulb

5. See diagram in attached file

a. Calculate the total resistance of the circuit, above and

b. the total current drawn from the supply

c. the voltage across the 8 ohm resistor.

#### Solution Preview

Please see the attached document..

(a) What is the difference between a scalar and a vector quantity?

Scalar quantities require only magnitude for their complete definition. For example, mass is a scalar quantity we just need to say only the figure like 45 or 10 kilograms.

Vector quantities require both magnitude and direction be specified. Force is a vector quantity, it requires both magnitude and direction as we say, 30 Newton acting downward/ upward/towards north/south etc.

7.21 km is the answer to section a)

b) See figure, direction is north east

c) Average velocity = total displacement/total time = 7.21km/2hr = 3.6 km/hr Answer

d) Average speed = Total distance/total time = 10km/2hr = 5km/hr

Q2

A car moves forward at 54 km/hr for 60 seconds; stops for 30 seconds; and then reverses

at 18 km/hr for 30 seconds

a) Sketch a velocity-time graph for this motion

b) Calculate the displacement of the car from its starting ...

#### Solution Summary

This solution address the kinematics and energy concepts and answers each question with a step-by-step manner. All formulas and calculations are shown.