# Physic lab questions

1. Oct 7, 2012

### bcalkins

Can you please help with the following problems? Formulas would be greatly appreciated or talking me through a problem. Thank you!!!

1.) A mass of 40 kg suspended from a 48-cm long light string forms a simple pendulum. The mass swings through the lowest point of its trajectory with a speed of 2 m/s. To what maximum height above the lowest point will it rise (in m)? (Neglect air resistance).

2.) A mass of 40 kg with an initial velocity of 1.6 m/s starts up a frictionless plane inclined at 20 degrees to the horizontal. To what maximum height (in m) above the base of the plane will the mass rise?

3.) You wind up and throw a 12 kg medicine ball horizontally with a speed of 1.9 m/s directly at your 21-kg little brother. The ball imbeds in your little brother’s mid-section and for a while afterwards they form a composite system.
What is the common speed of the ball-brother composite immediately after impact (in m/s)?

4.) A rectangular crate, 4 m × 1 m × 1 m, has a mass of 26 kg. It is originally standing on one of its square sides on the floor, and a person places it on one of its rectangular sides on top of a 3 m high table. How much mechanical work (in J) has been done by this person to achieve this change in position? Assume the mass of the crate is uniformly distributed throughout its volume. (Hint: Refer to the discussion of center of mass in the experiment description.)

Thank you VERY much!

2. Oct 8, 2012

### tiny-tim

hi bcalkins!

for 1) 2) and 3), use conservation of energy or of momentum

show us what you get