Written Questions

1.) If you push forward on the back of a car, does that mean that its velocity has to be

in the forward direction? Explain and give an example.

2.) A physics book is motionless on the top of a table. If you give it a hard push with

your hand, it slides across the table and slowly comes to a stop.

Use any of Newton's Laws of motion to answer the following.

a)Why does the book remain motionless before the force is applied?

b)Why does the book move when the hand pushes it?

c)Why does the book eventually come to a stop?

d)Under what conditions would the book remain in motion at a constant speed?

3.) A box has a mass of 3.0 kg. What would be the mass of the box if it was taken

to Jupiter where the acceleration due to gravity is ten times that of Earth?

4.) Compare the force needed to lift a 10 kg rock on Earth and on the moon.

Compare the force needed to throw the same rock horizontally at the same

speed in the two locations.

5.) Why does a package on the seat of a bus slide backward when the bus accelerates

quickly from rest? Why does it slide forward when the driver applies the brakes?

Problems

1.) A truck and its load have a mass of 1875 kg. What is the

net force required to accelerate it at 3.86 m/s^{2}, west? S

2.) Find the mass of a car that requires a net force of 5.31 kN, north

to slow it to a stop from 115 km/h, south in 9.47s. S

3.) Find the force of friction acting on a piano if the applied forces are

2.22 x 10^{2} N, south and 176.8 N, north and it is travelling at constant speed. S

4.) Find the applied force on a 40.5 kg loaded shopping cart if it

accelerates at 1.02 m/s^{2}, east when the force of friction is 3.56 N. S

5.) Find the mass of a bar of steel whose weight is 36.70 N. S

6.) A 14.6 kilogram monkey hangs from a vine.

What force does the vine exert on the monkey? S

7.) A squirell of mass 1.40 kg throws a 125 g nut with a force of 0.43 N, south.

Find the acceleration of both nut and squirell ignoring friction. S

8.) A 90.0 kg man climbs at a constant velocity up a ladder. S

a) What force does the ladder exert on the man?

b) What force does the man exert on the ladder?

c) How would the answers to a) and b) change if he was descending?

9.) An ascending 485.0 kg hot air balloon rises due to 5.12 kN of upward lift.

Find its acceleration. S

10.) What applied force is necessary to keep a 10.0 kg box moving at a constant velocity

of 5.5 m/s, west along a surface with a sliding coefficient of friction of 0.36? S

11.) The coefficient of sliding friction between rubber tires and dry pavement is 0.80. S

The brakes are applied to a 1200 kg car traveling north and it skids to a stop.

a) Find the force of friction the road exerts on the car.

b) Find the acceleration of the car. Would it be constant?

## Answers