Question

A contestant in a winter games event pushes a 35.0-kg block of ice across a frozen lake with a force of 25 N at 28.0° below the horizontal as shown in Figure (a) below, and it moves with an acceleration of 0.630 m/s2 to the right. (a) What is the normal force exerted by the lake surface on the block of ice? (b) Instead of pushing on the block of ice, the contestant now pulls on it with a rope at the same angle above the horizontal as in part (a), and with the same magnitude of force. See Figure (b) above. Now what is the normal force exerted by the lake surface on the block of ice?

Answer 1

Given

m = 35 kg

F = 25 N

θ = 28

a = 0.630 m/s2

Procedure

(a) What is the normal force exerted by the lake surface on the block of ice?

Now, let's calculate the summation on the y-axis.

$\begin{gathered} N-mg-F\cdot\sin 28=0 \\ N=mg+F\cdot\sin 28 \\ N=35kg\cdot9.8m/s^2+25N\cdot\sin 28 \\ N=354.74\text{ N} \end{gathered}$

(b) Instead of pushing on the block of ice

Now, let's calculate the summation on the y-axis.

$\begin{gathered} N-mg+F\cdot\sin 28=0 \\ N=mg-F\cdot\sin 28 \\ N=35kg\cdot9.8m/s^2-25N\cdot\sin 28 \\ N=331.26\text{ N} \end{gathered}$