Physics Answers

A convex mirror has a focal length of -0.90 m. An object with a height of 0.40m is

2.4m from the mirror. GRASP method.

a) Calculate the image distance.

b) Calculate the image height.

What is the force exerted by Big Ben on the Empire State building? Assume that Big Ben

has a mass of 108 kilograms and the Empire State building 109 kilograms. The distance

between them is about 5000 kilometers and Big Ben is due east of the Empire State

building.

how does the velocity of a freely falling body change in time

Water is flowing in a fire hose with a speed of 1.0 m/s with a height of 3.0 m and a pressure of 200,000 Pa. You lift the nozzle of the hose to a height of 1.5 m above the ground. At what speed does the water now come out of the hose?

A particle is moving along the x-axis. Its acceleration is given by 𝑎𝑥 = 𝑐𝑡 − 𝑑𝑡²

with c=2.0m/s³and d=0.24m/s⁴.The particle is at rest at the origin at t=0. Find position and 

velocity as functions of time. What is the maximum velocity the particle reaches?

A particle is moving along the x-axis. Its position as a function of time is given as

𝑥 = 𝑏𝑡 − 𝑐𝑡²

.

a) What must be the units of the constants b and c, if x is in meters and t in seconds?

b) At time zero the particle is at the origin. At what later time t does it pass the origin again?

c) Derive an expression for the x- component of velocity.

d) At what time t is the particle momentarily at rest?

e) Derive an expression for the x-component of the particle’s acceleration, ax.

A wheel of radius 14.0 cm starts from rest and turns through 2.0 revolutions

in 3.0s.

a. What is its average velocity?

b. What is the tangential velocity of a point on the rim of the wheel?

A mass of 0.30 kg attached to a vertical spring, stretches the spring by 10 cm. Find

(a) the spring constant k.

(b) Work done by gravity and the spring force.

(c) the maximum restoring force.

(d) What is the change in gravitational potential energy?

A block of mass m = 12 Kg is pushed at a constant speed, up an incline plane (angle of

inclination 30o

) though a distance of s= 4.5m and raised to a height h= 2m. The coefficient

of kinetic friction between the block and the incline is 0.41. Calculate the work done by

(a) Normal force

(b) the external force applied parallel to the incline.

(c) gravity

(d) the frictional force.

What is the length of a simple pendulum used in a grandfather clock that has one second between it's tick and it's tock on Earth?