Homework Answers

A. An object of mass m is placed on an inclined plane with a rough surface. Derive an

equation of the acceleration of the object sliding down the incline. [Be sure to

include an appropriate diagram highlighting the relevant forces] (10 marks)

B. A train of mass 200kN has a frictional resistance of 5N per kN. The speed of the

train, at the top of an inclined of 1 in 80 is 45 km/h. Find the speed of the train after

running down the incline for 1km. (10 marks)

A student builds and calibrates an accelerometer, which she uses to determine the speed of her

car around a certain unbanked highway curve. The accelerometer is a

plumb bob with a protractor that she attaches to the roof of her car. A friend riding in the car

with her observes that the plumb bob hangs at an angle of 15.0° from the vertical

when the car has a speed of 23.0 m/s.

A. What is the radius of the curve? (8 marks)

B. What is the centripetal acceleration of the car rounding the curve? (7 marks)

C. What is the speed of the car if the plumb bob deflection is 9.00° while

rounding the same curve? (5 marks)

A body of mass 25kg falls on the ground from a height of 19.6m. The body penetrates into the

ground. Assume the resistance by the ground to penetrate is constant and equal to 4998N.

Take g = 9.8m/s2

.

A. Find the final velocity of the body just before it hits the ground. (8 marks)

B. Calculate the retardation (acceleration) when the body is penetrating the ground.

(7 marks)

C. Find the distance through which the body will penetrate into the ground.

(5 marks)

An object of mass m is placed on an inclined plane with a rough surface. Derive an equation of the acceleration of the object sliding down the incline. [Be sure to include an appropriate diagram highlighting the relevant forces] 

An airliner must reach a speed of 110 m/s to take off. If the available runway is 2.4 km and the aircraft accelerates uniformly from rest at one end, what minimum acceleration must be available if it is to take off?

1.) In uniform circular motion, frequency is

a. Zero

b. Constant, nonzero

c. Increasing

d. Varying

2.) The following are the units of frequency, except for

a. Meter per second

b. Cycles per second

c. cps

d. Hertz

3.) Position angle is the ratio of the arc length and radius. If an object in non-uniform circular motion with 2-m radius circular path is at

position angle of 300 radians. find the arc length covered.

a. 300 m

b. 150 m

c. 75 m

d. 600 m

1.) A projectile is directed toward the sky with an angle of 45° from the level ground. It reaches a range of 10m in 10s. While in air, the projectile's horizontal acceleration is

a. - 9.81 m/s²

b. +9.81 m/s²

c. + 9.81 m/s²

d. 0

2.) If you launch one at an angle 45 degrees and another at 30 degrees, which angle gives you longer range?

a. both angles give same range

b. 45 degrees

c. 30 degrees

3.) A projectile is given a horizontal velocity. As it moves, its vertical speed

a. decreases

b. increases

c. fluctuates

d. remains constant

4.) For an object in uniform circular motion, what effect would be produced on the magnitude of the centripetal acceleration of the object if the mass of the object triples.

a. Quadruples

b. 1/2 as big

c. No change

d. Doubles