I'm real rusty on my physics, but here are five simple sample problems we were given, I'd appreciate your help in helping me solve these. Thanks!(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

(1) A single horizontal 10.0 N force, F acts on a 2.0 kg block which is initially at rest at x=0 m. In response to the force, the block accelerates in the direction of the force and some time later has travelled 20.0 m. Use this information to answer the following three questions:

a. In moving through the 20.0 m displacement, the force F does an amount of work given by?

b. What was the horizontal acceleration of the block in m/s2?

c. What was the speed (in m/s) of the block when it passes the x=20.0 m mark?

(2) Suppose that a computer hard drive has a disk that rotates at a constant speed of 7200 rpm (revolutions per minute).

a. What is the direction of acceleration of a point 2.0 cm from the axis of this rotating disk?

b. What is the magnitude of the acceleration (in m/s2) of a point 2.0cm from the axis of rotation?

(3) Suppose the mass of a 1.0 g match was converted entirely to energy. How many Joules of energy would this create?

(4) A spring with constant 2.0 N/m stores 16.0 J of energy when it is compressed by what distance?

(5) A block of mass M falls a distance D near the surface of the earth and reaches a speed V. What is the final speed of an identical block which falls a distance 16D?[/B]

2. Relevant equations

F=ma

KE=1/2mv²

a=v²/r

W=FD

W=1/2kx²

s=d/t

yf=yi+vit+1/2at²

3. The attempt at a solution

1) A single horizontal 10.0 N force, F acts on a 2.0 kg block which is initially at rest at x=0 m. In response to the force, the block accelerates in the direction of the force and some time later has travelled 20.0 m. Use this information to answer the following three questions:

a) In moving through the 20.0 m displacement, the force F does an amount of work given by?

W=FD

200N·M=10N*20m

b) What was the horizontal acceleration of the block in m/s2?

f/m=a

10N/2kg=5m/s²

c) What was the speed (in m/s) of the block when it passes the x=20.0 m mark?

KE=1/2mv² and I need to think about conservation of energy, and I know s=d/t but I need time... t=d/s but I need speed... hrrm.

2) Suppose that a computer hard drive has a disk that rotates at a constant speed of 7200 rpm (revolutions per minute). What is the direction of acceleration of a point 2.0 cm from the axis of this rotating disk?

This must be toward the axis of rotation?

b) What is the magnitude of the acceleration (in m/s2) of a point 2.0cm from the axis of rotation?

a=v²/r

2cm=.02m

2πr?? involved I really don't know how to approach this one.

3. Suppose the mass of a 1.0 g match was converted entirely to energy. How many Joules of energy would this create?

A lot... I know that..

4. A spring with constant 2.0 N/m stores 16.0 J of energy when it is compressed by what distance?

x=f/k

8m=16/2 ...right?

5. A block of mass M falls a distance D near the surface of the earth and reaches a speed V. What is the final speed of an identical block which falls a distance 16D?

iv+at for the vf of free-falling objects

xi=xf+vit+1/2at² for the position of free-falling objects.

so 16 times the speed would be 16 times the distance.. I think.

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# Homework Help: A couple Force, work, KE, and spring problems I'm working on.

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