Mechanics | Relativity Answers

A student pushes against a wall with a force of 300 N for 10 seconds. What is the work done on the wall by the student?

A student’s iPhone 6 (mass = 0.129 kg) is tied to a 40 cm string and rotated at a constant speed of 5.0 m/s in a circular path.

a) What is the magnitude of the iPhone’s centripetal acceleration?


b) Find the magnitude of the centripetal force on the iPhone.

Which way does the centripetal force point for an object undergoing uniform circular motion?

A rectangular brass bar of mass M has dimensions a,b,c. The moment of inertia I is given by
I = M(a squared + b squared)/12 and the following measurements are made:
M= 135.0 +/- 0.1 g
a= 80 +/- 1 mm
b= 10 +/- 1 mm
c= 20.00 +/- 0.1 mm

Calculate the standard error in
1) Density p of material
2) Moment of Inertia I

My answers:
1) 8,4375 * 10 ( to the power -6)
2) Inertia I got 73,125 kg.m (squared) and standard error i struggled with.

Please assist and confirm whether or not my answers are correct.

1.explain why it's not safe for passengers to stand on the upper decker in a double decker bus
2.a uniform rule is balanced at 30cm mark when a mass of 50g is hanging from it's zero mark.calculate the weight of the rule

A 0.5 kg water balloon is dropped from a balcony 40 meters from the ground. What is the balloon's velocity just as it hits the ground? (Ignoring air resistance)

describe how you could use a piece of paper, a coin and a desk to demonstrate newton's first law for an object initially at rest. include an explanation of how this this demonstrates The law

You and your little brother are shifting a large 58 kg rock by carrying it together on a 3.0 m long litter.
Your little brother is capable of exerting an upwards force of 100 N on one end of the litter.

How far should the rock be placed from you in order for you and your brother to carry the litter without it tipping? (in m to 2 s.f)

An inclined plane reduces the effort force by

A balloon remains stationary about 100 m above the ground. State what forces are acting on the balloon and explain how they result in no motion