PHY_10_V1_DM_Revision term 1 (1)

Kinematics:

1.      The position as a function of time of an object moving along x – axis is presented by the graph above. Which of the following statements is true?

(A) The velocity of the object is zero.

(B)  The acceleration of the object is zero.

(C)  At time t = 0 the object is at the origin.

(D) The acceleration of the object is a positive constant.

2.      An object accelerates from rest at a constant rate. Which of the following graphs could be used to describe the motion of the object?

(A)                                                                               (B)

(C)                                                                               (D)                           

Dynamics:

3.      According to Newton's second law, the modulus of force F acting on a body is determined by the formula:

a.   

b.  

c.      

d.  

4.      What is the modulus of the resultant force, if under their action a body weighing 6 kg moves with an acceleration of 1.5 m / s²?

5.      The figure shows the forces acting on a body weighing 3.5 kg. Determine the modulus of acceleration of the body under the action of these forces, if the modulus of force F2 = 21 N. 

6.       

A ball thrown horizontally from a steep rock with an initial velocity of 20 m / s modular fell to the ground 40 meters from the base of the rock. What is the height of the rock?

7.      The body slides off an inclined plane that makes an angle of 300 with the horizon. What is the coefficient of sliding friction, if the acceleration modulus of the body is equal to 3.2 m / s²?

8. A child standing on the edge of a freely spinning merry-go-round moves quickly to the center.   Which one of the following statements is necessarily true concerning this event and why?

a.       The angular speed of the system decreases because the moment of inertia of the system has increased.

b.      The angular speed of the system increases because the moment of inertia of the system has increased.

c.       The angular speed of the system decreases because the moment of inertia of the system has decreased.

d.      The angular speed of the system increases because the moment of inertia of the system has decreased. 

e.       The angular speed of the system remains the same because the net torque on the merry-go round is zero N × m.

9.      What happens when a spinning ice skater draws in her outstretched arms?

a.       Her angular momentum decreases.

b.      Her angular momentum increases.

c.       Her moment of inertia decreases causing her to speed up.  

d.      Her moment of inertia decreases causing her to slow down.

e.       The torque that she exerts increases her moment of inertia.

Hydrostatic Pressure:

1.      Orlik Dam is the largest dam in the Czech Republic in terms of the capacity of water which the dam contains. The bottom of the dam is 275 meters above the sea level, , and  the maximum allowed height of the water level is 354 meters above the sea level. The area of the dam is approximately 2730 ha.  During a flood in 2002 the maximum allowed height of water level was exceeded by 2.0 meters. Determine the pressure of the water at the bottom of the dam.

Pascal’s Law:

1.      When you take your car into the shop to have it worked on, a hydraulic lift is used. The diameter of the piston lifting your car is 2.5 m, while the input piston has a diameter of only 0.1m.  Your car and the base it sits on have a combined mass of 1200kg. The oil used in this lift has a density of 800kg/m³. 

How many Newton’s of force will you need to exert on the input piston in order to hold your car in place. 

How many Newton’s of force will be required to lift your car to a height of 1.5 m?

2.      A trash compactor pushes down with a force of 500 N on a 3 cm² input piston, causing a force of 30,000 N to crush the trash. What is the area of the output piston that crushes the trash?

Archimedes’ Principle:

1.      What volume V of helium is needed if a balloon is to lift a load (including the weight of the empty balloon) of 180 kg? 

2.      Why is swimming in the ocean easier than swimming in a river or a lake?  Salt water has a higher density than fresh water, so the buoyant force is greater.

3.      A block of mass 360 g weights 3 N in water and 2.4 N in liquid A. Find the density of liquid?