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July 4, 2015

Homework Help: grade 11 physics

Posted by Sarah N H on Sunday, January 24, 2010 at 2:00pm.

Cathy takes the bus home from work. In her hand she holds a 2 kg cake box, tied together with a string. As she ascends the steps into the bus,the box accelerates upward at a rate of 2.5m/s^2. what is the force exerted on the string?

Fg=ma
=2*9.8
=19.6N

Fn=ma-Fg
=2*2.5-(-19.6)
=24.6N

b)she sets the box on the seat beside her. the bus acelerates from rest to 60 km/h in 4 s and the box begins to slide. What's the coefficient ofstatic friction b/w the box and te bus seat?

Ff=m*Fn
=2(24.6)
=49.2N

static coefficient=Ff/Fn
=49.2/24.6
=2

c)a taxi suddenly cuts infront of the bus, causing the bus driver to slam on the brakes. The bus driver reduces the speed from 60 km/h to 20 km/h in 1.5 s. Does Cathy's cake slide forward?
I have no idea how to even start with this one.

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