Midterm exam

Midterm exam

Question 1

The earth is round because of gravitational force that squeezes the earth into a circular shape. Though the earth is spherical, it is not a perfect sphere. The earth bulges at the equator and flattens at the poles, making it an imperfect sphere. Bulging at the equator is caused by centrifugal force, while centripetal force causes flattening at the poles. The imperfect sphere shape of the earth is called an oblate spheroid.

Question 2

• Initial velocity u, = 2m/s

Acceleration a, = 1 m/s/s

Final speed v, = 5m/s

Substitute these values using the first equation of motion

V = u + at, t = time

t = v-u/a

t = 5-2/1

T=t = 3 seconds

(b) How far did it go?

To get the distance, use the third equation of motion, v = u2 + 2ad

D = V²– u²/2a

D = (5)² – (2)²/2 X 1

D = 10.5 m

Question 3

Newton’s law of attraction states that the force of attraction between two objects is directly proportional to the product of the masses and inversely proportional to the square distance between them. It is given by the formula, F = G (m1m2)/R²

Question 4

Five steps

1. Ask questions
2. Do background research

• Formulate a hypothesis

1. Experiment
2. Draw a conclusion

Question 5

Centripetal force is given by F_c=mv²/r

M = 1kg

V = 10m/s

R = 1 m

F = 1 X 10²/1

F = 100N

Question 6

Mass is a property of matter measured in grams or kilograms and is the same everywhere. On the other hand, weight is the measure of the gravitational force on a body, measured in Newton (N), and varies from one location to another.

Question 7

Since the apple is dropped, its initial velocity is = 0

Time taken = 5 seconds

Height of the window, h =?

h = 1/2gt²

= 1/2 *9.8*5²

= 122.5 m

The height of the window is 122.5 m

Question 8

Work done is given the product of mass, acceleration, height.

Given

The applied force F = 100 N

Mass of the box, m = 20 kg,

Displacement, s = 10 m

Work done by the force on the box is W =?

Work done is given by W = F. S = F*S cos theta

Here theta is zero both the displacement and force are in the same direction so cos 0 = 1

• W = FX s

W= 100 X 10 = 1000J

• Work done is given by the gravitational potential energy attained by the box after being raised a distance of 10 m

W = m X g X h whereby m = 20, g = 9.8, h = 10

W = 1960J

Thus, the work needed to raise the same box by 10 m is 1960 Joules.

Question 9

Power = W/t

T = W/power

T = f*d/power

T = mg*d/power

T = 900 * 9.8* 30/15000

= 17.64 seconds

Question 10

Kinetic energy, KE = 1/2MV² whereby m= 1000kg, V = 10m/s/s

KE = ½ X 1000 X 10²

= 1000 x 100/2

KE = 50, 000 J

Question 11

PEG = m g h

PEG = potential energy due to gravity

g = acceleration due to gravity

m = mass

Delta h = distance above a surface (such as the ground)

Substitute the values, m = 1000kg, h= 45m, g = 9.8 N/Kg

PE_G = 1000 X 9.8 X 45

= 441,000 Joules

Question 12

Global warming is the gradual increase in the average temperature of the earth due to an increase in concentrations of greenhouse gases in the atmosphere.

One of the reasons why global warming is causing a rise in sea level is because as the temperatures rise and the world is gradually becoming warmer, the high temperatures cause the melting of glaciers and snow. When the glaciers melt, the water finds its way to the oceans and seas hence causing the level of the sea to rise. Secondly, due to the high global temperatures caused by global warming, seawater expands. As the water expands, it takes up more space in the ocean basin, causing a rise in water level.

Question 13

Mass = 80 kg

Change in temperature (delta) t = (100 – 20) = 80

Specific heat capacity C = 4.2 KJ/kg degrees Celsius

Heat required = m * C* delta t

80 * 4.2 * 80

26,880 KJ