i have a test tomorow and I am having trouble with these questions can some one pls check over my answers?(adsbygoogle = window.adsbygoogle || []).push({});

1. a slingshop shoots a 12g stone at 36m/s. It goes in an arc and at the top of the arc it is going at 14m/s. How high is it at this point?

12g=0.012kg

36m/s=v1

14m/s=v2

Ek=1/2mv2

=1/2(0.012kg)(36m/s)2

=0.216J

Eg=mgh

0.216=0.012kg(9.8m/s)h

0.216J

0.1176

=1.8m

the hight is 1.8m

2. A child of 27kg climbs to the top of a 5.0m high playground slid

A) what is her potentian energy?

27kg=m

5.0m=h

Eg=mgh

=27kg(9.8m/s)(5.0m)

=1323J

the potential energy is 1323J

B)Her actual speed at the bottom is only 3m/s. According to conservation of energy how fast should se be going?

Ek=1/2mv2

=1/2(27kg)v2

1323/13.5=v2

98=v2

9.9=v

she should be going 9.9m/s

C) the slid is 8.0m long. determine the force of friction acing

d=8.0m

Ff=?

d=(v2+v1/2)t

t=1.6s

a=v2-v1/t

a=9.9m/s-0m/s/1.6s

a=6.2m/s2

F=ma

27kg(6.2m/s2)

F=167.4N

the force of friction is 167.4N

3. A 72kg passenger is in a van moving at 15m/s when it colides with a wall. The frount part of the van collapses 0.50m during the crash. determine the work done on the passenger and the force the seatbelt exerts during the acident.

72kg=m

15m/s=v1

0.50m=d

w=?

Ff=?

Ek=1/2mv2

=1/2(72kg)(15m/s)2

=8100J

...now what??????

4/ A roler coaster has a height of 94.5m above the ground at its highest point. deteremine the maximum speed of the cars as they come down from this high point. the actual speed is 41.1m/s. Calcuate the work done by friction.

Eg=mgh

=1kg(9.8m/s2)(94.5m)

=926.1J

Ek=1/2mv2

926.1=1/2(1kg)v2

926.1/0.5=v2

1852.2=v2

43m/s=v

the maximun speed it 43m/s

i dont know how to calculate the force of friction

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# Homework Help: Kinematics of a slingshot

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