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Physicshelpline

. February 2017

Projectile Motion

(On request - Tamanna)

Q- A ball is thrown vertically upward from a window at 10 m/s at an angle of 45° to the horizontal. It hits the ground 5.0 s later. 
a) What is the vertical height of the window from the ground? 
b) How far from the base of the building does the ball strike the ground? 

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Simple Harmonic Motion

Q- A bungee jumper whose mass is 95 kg, has just completed his first bungee jump and is now bouncing up and down at the end of the cord. His oscillations have initial amplitude of 7 m and a period of 4.0 s.

(a) What is the spring constant of the bungee cord?

(b) What is the jumper's maximum speed …

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Electrostatics: Capacitors

Q- Two capacitors C1 = 30 µF and C2 = 60 µF are connected in series with a 12 V battery. Find

(a) The charge on C1 and

(b) The potential difference across C2.

Solution:

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Circular Motion

Q- A space station, in the form of a wheel 120m in diameter, rotates to provide an "artificial gravity" of 3.00m/s2 for person's who walk around on the inner wall of the outer rim. Find the rate of rotation of the wheel (in revolutions per minute) that will produce this effect.

Solution:

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Magnetic Field

Q- Two very long coaxial cylindrical conductors are placed with their axes coincide with z axis. The inner solid cylinder has radius a = 2 cm and caries a total current of I1 = 1.2 A in the positive z-direction. The outer cylinder has an inner radius b = 4 cm, outer radius c = 6 cm and carries a cu…

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Sound Waves: Doppler Effect And Beats

Q- A trumpet player is on a flatcar drawn by a locomotive and another player is near tracks. If each player blows a 440 Hz note, and if there are 4 beats/s as they approach each other, what is the speed of the flatcar? (Speed of sound in air is 340 m/s)

Solution:

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Ray Optics: Concave Mirror

Q- An object is placed a distance r in front of a wall where r is exactly equals the radius of curvature of a certain concave mirror.

(a) At what distance from the wall the concave mirror to be placed so that a sharp image of the object is formed on the wall?

(b) What is the magnification of this …

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Rotational Motion: Moment of Inertia

Q- A car tire of inner radius 16.5 cm and outer radius 30.5cm is modeled as having two sidewalls of uniform thickness 0.635cm and a tread wall of uniform thickness 2.50cm and width 20.0cm over it. Assume the rubber has uniform density equal to 1.10 x 103 kg/m3, find its moment of inertia about an ax…

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Electromagnetism: Induced EMF

Q- A solenoid has length L = 30 cm, radius 6 cm, and N1 = 5500 turns; its axis coincides with the z-axis. A circular conducting loop containing N2 = 15 turns of radius a = 3 cm is centered inside the solenoid; the plane of the loop makes a 30° angle with respect to the z-axis. The loop has a net res…

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Work Power Energy

Q- A 150 m long rope of mass 250 kg is wrapped on a spool and its 50.0 m is hanging vertically. Now the spool is rotated to pull the rope up slowly. How much work is to be done to pull further 20.0 m of the rope? Neglect any friction force. 

Solution:

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Sound: Shock Cone

Q- A person looks directly overhead and sees a plane exactly 1.5 km above the ground flying faster than the speed of sound. By the time he hear the sonic boom, the plane has traveled a horizontal distance of 2.0 km.

(a) Find the angle of the shock cone.

(b) Find the speed of the plane (the Mach nu…

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Gas Laws

Q- At some place the temperature of air is 20 degrees C and the pressure is 1.021*105 Pa. Calculate the density of air.

Solution:

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Capacitor

Q- A capacitor stores 135 J of energy when it is charged to 300 V

(a) What is the capacitance of the capacitor?

(b) How much charge must be transferred from one plate to the other to store this energy? 

Solution:

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Simple Harmonic Motion

Q- A 240 g mass suspended by a 0.8 m long string is pulled 8.4° to one side and released. How long does it take for the pendulum to reach 6.0° on the opposite side? 

Solution:

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Electrostatics: Electric Field

Q- Three charges are placed at the vertices of an equilateral triangle of side a = 6 cm. qA = +3 µC, qB = +3 µC, and qC = -3 µC.

(a) Find the x- and y- components of the electric force acting on qC

(b) Find the electric field at the position of qC due to qA and qB.

Solution:

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Motion in a plane

Q- An object is accelerating along x axis with an acceleration of 2 m/s2 for three 3 s and attaining a velocity of 20 m/s at an angle of 300 with positive x direction.

(a) Calculate magnitude of initial velocity of the object.

(b) Find the direction of initial velocity vector.

Solution:

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Induced EMF in an Inductor

Q4. A current i through a 0.5 H inductor vary with time t as shown by the graph below. Find the magnitude of the induced emf for the time interval

(a) t = 0 to t = 2 ms. You can ignore the behavior at the ends of the intervals. 

(b) t = 2 to t = 5 ms.

(c) t = 5 to t =6 ms.

Solution:

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Standing Waves

Q- A steel wire having a mass of 5 g and a length of 1.2 m is fixed at both ends and has a tension of 974 N.

(a) Find the speed of transverse waves on the wire.

(b) Find the wavelength of the fundamental.

(c) Find the frequency of the fundamental.

(d) Find the frequency of the second harmonic.

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