C Exercise 6.30

Part A = 230Ns

Part B = 780N

Part C = The other car exerts this force on the driver.

Solutions Below:

^{2}.

Part A

Express your answer using two significant figures.

Impulse is just FΔt:

I = FΔt

F = ma

F = 46 * 17

F = 782

I = 782Δt

I = 782 * 0.30

I = 234.6

I = 230Ns (2 significant figures)

Part B

Express your answer using two significant figures.

Be careful here. My first reaction was to find average force by dividing 782N (46kg * 17m/s^{2} by 0.3s (Δt). But this isn’t correct. What you have to consider is that the force is 782N, period – and that it’s applied on the driver for 0.3s. Since the force is constant, the average force is just the force. To make an analogy, consider acceleration due to gravity, which is -9.8m/s^{2} (the average would be -9.8m/s^{2} regardless of how long something accelerated for).

F = 780N (2 significant figures)

Part C

The other car exerts this force on the driver.

Could I get some help with these problems please?

Problem 6.37

A 71kg trampoline artist jumps vertically upward from the top of a platform with a speed of 4.7m/s .

(a)What is his speed as he lands on the trampoline, 2.2m below his jump off point?

(b)If the trampoline behaves like a spring with spring stiffness constant 7.1×104N/m , how far does he depress it? Any depression of the trampoline from equilibrium is to be taken as a negative distance.

Problem 6.73

In a certain library the first shelf is 15.0cm off the ground, and the remaining four shelves are each spaced 31.0cm above the previous one.

(a)If the average book has a mass of 1.4kg with a height of 22cm , and an average shelf holds 29 books, how much work is required to fill all the shelves, assuming the books are all laying flat on the floor to start?

Thanks!

We posted answers to these problems here and here. Good luck!