Question

1. The current cost of energy consumption is $0.25 per kWh. An air conditioner uses 7.000 W for 8 h . Determine the total cost for turning the air conditioner on for that time

a) None of the choices

b) $5.60

c) $ 14.000

d) 14.00

2) A ball is thrown up with an initial speed of 39.2 m/s. Determine the object's maximum height.

a) 78.4 m

b) none of the choices

c) 34.3

d) 9.8

3.Determine the critical angle for total internal reflection as light travels from polystyrene ( n=1.49 ) to air ( n=1 . Round your answer to the nearest degree.

a)60 °

b) 42 °

c) 90 °

d) 21°

4.The speed of a wave on a string is 40 m/s . If the frequency is 100 Hz, find the wavelength.

a) 40 m

b) 40 cm

c) 4 km

d) 20 m

5. Which wave has the greatest speed .

a) gamma ray

b) all electromagnetic waves travel at the speed of light.

c) ultra-violet

d) visible

Answer 1

1. Current cost per energy consumption is $0.25 per kWh.

No.of watts used is 7 watts

Time is 8 hrs

KWh = watts×hours/1000

KWh = 7×8/1000

KWh=0.056kWh

Current cost is 0.056×0.25= $0.014.

So answer is (a) none of the choices

2. Initial speed ,u=39.2 m/s

Acceleration due to gravity,g=9.8m/s²

Maximum height reached by the object,H=u²/2g

H=(39.2)²/2×9.8

H=78.4m

Ans_ (a) 78.4m

3. Light travels from polystyrene to air

n of polystyrene,n1= 1.49

n of air ,n2= 1

Critical angle,c = sin-¹(n2/n1)

C= sin-¹(1/1.49)

C= sin-¹(0.67)

C= 42°

Ans_ (b) 42°

4. Speed of wave,v= 40m/s

Frequency,f= 100Hz

Wavelength,λ= ?

v= fλ

λ= v/f

λ= 40/100

λ= 0.4 m= 40 cm

Therefore, wavelength of the wave on the string is 40cm.

Ans _ (b) 40 cm

4 . (b) All electromagnetic waves travel at the speed of light.