Physics Answers

An apple is falling down from a height of 20m and then hit a

person. Assume that the mass of the apple is 200g. The

duration of impact is 0.001 sec and that the area of the

bone is 1 cm². (a) Calculate the impulsive force applied to

the person. (b) If the rupture strength for body tissue is

about 5 X 10⁶ dyn/cm² will the impact force lead to serious

injury for the person?

In a car collision, the bag expands suddenly and cushions

the impact of the passenger. Assume the impact velocity is

105 km/h. For a 70-kg person with a 30-cm allowed

stopping distance, (a) calculate the stopping force per cm²

applied to the person, if the average applied force is

uniformly distributed over a 1000-cm² area of the

passenger's body. (b) calculate the duration of the collision

between the passenger and the inflated bag of the collision

protection device. (c) If the rupture strength for body tissue

is about 5 X 10⁶dyn/cm², will the impact force lead to

serious injury for the passenger?

Sound waves in air are [Best answer].

A. Transverse waves

B. Longitudinal waves

C. Shear waves

D. Stress waves

A planet with a mass of 5.51x10²⁴kg and a radius of 6.36x10⁶m orbits its sun, a distance of 139.4x10⁹m away, in a uniform circular motion with velocity 3.42x10⁴m/s. Assuming the planet is a uniform solid sphere spinning on its axis and has the same length of day as Earth, what is the orbital angular momentum of this planet (in kg⋅m²/s)?

A metal bar is of length 2.0m and has a square cross-section of side 40mm. when a tensile

force of 80KN is applied, it extends by 0.046mm. Calculate (a) the stress (b) the strain in the

specimen

Exercise 7

1. When 1.5kg of water is converted to steam (at 1000

c) at STP, 3.39MJ of heat are required.

During the transformation from liquid to vapour state, the increase in volume of the water

is 2.5m3

. Calculate the work done against the external pressure during the process of

veporisation. Explain what happens to the rest of energy.

The voltmeter reading across R1 is 2,70 V. How will the voltmeter reading change

if R3 is removed? Write INCREASE, DECREASE or REMAINS THE SAME AND explain your answer.

A

surface of the earth. When the satellite orbits around the earth at a height equal to the diameter of the earth (above the surface of the earth), the magnitude of the gravitational force on the satellite will be:

satellite experiences a gravitational force with magnitude F when it is on the

A 3F

B 2F

C 1/3 F

D 1/9 F

Consider the following statements with regard to Newton’s third law of motion:

I: The resultant of an action-reaction force pair is zero.

II: An object moves when the action force is larger than the reaction force.

III: The resultant of an action-reaction force pair cannot be determined, because

the force acts on different objects.

Which statement(s) above is/are correct?

A Only I

B Only II

C Only III

D Only II & III

Two forces, 3 N and 5 N respectively, act on the same point simultaneously. The magnitude of their resultant force is 2 N when the angle between them is _____.